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129 KiB
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<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>JEMALLOC</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry"><a name="idp45223136"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>jemalloc — general purpose memory allocation functions</p></div><div class="refsect1"><a name="library"></a><h2>LIBRARY</h2><p>This manual describes jemalloc 4.0.3-0-ge9192eacf8935e29fc62fddc2701f7942b1cc02c. More information
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can be found at the <a class="ulink" href="http://www.canonware.com/jemalloc/" target="_top">jemalloc website</a>.</p></div><div class="refsynopsisdiv"><h2>SYNOPSIS</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <<code class="filename">jemalloc/jemalloc.h</code>></pre><div class="refsect2"><a name="idp44244480"></a><h3>Standard API</h3><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">malloc</b>(</code></td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">calloc</b>(</code></td><td>size_t <var class="pdparam">number</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">posix_memalign</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">aligned_alloc</b>(</code></td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">realloc</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">free</b>(</code></td><td>void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="refsect2"><a name="idp46062768"></a><h3>Non-standard API</h3><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">mallocx</b>(</code></td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">rallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">xallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">extra</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">sallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">dallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">sdallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">nallocx</b>(</code></td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">mallctl</b>(</code></td><td>const char *<var class="pdparam">name</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">oldp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">oldlenp</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">newp</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">newlen</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">mallctlnametomib</b>(</code></td><td>const char *<var class="pdparam">name</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">mibp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">miblenp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">mallctlbymib</b>(</code></td><td>const size_t *<var class="pdparam">mib</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">miblen</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">oldp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">oldlenp</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">newp</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">newlen</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">malloc_stats_print</b>(</code></td><td>void <var class="pdparam">(*write_cb)</var>
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<code>(</code>void *, const char *<code>)</code>
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, </td></tr><tr><td> </td><td>void *<var class="pdparam">cbopaque</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">opts</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">malloc_usable_size</b>(</code></td><td>const void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">(*malloc_message)</b>(</code></td><td>void *<var class="pdparam">cbopaque</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">s</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><p><span class="type">const char *</span><code class="varname">malloc_conf</code>;</p></div></div></div><div class="refsect1"><a name="description"></a><h2>DESCRIPTION</h2><div class="refsect2"><a name="idp46115952"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) function allocates
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<em class="parameter"><code>size</code></em> bytes of uninitialized memory. The allocated
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space is suitably aligned (after possible pointer coercion) for storage
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of any type of object.</p><p>The <code class="function">calloc</code>(<em class="parameter"><code></code></em>) function allocates
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space for <em class="parameter"><code>number</code></em> objects, each
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<em class="parameter"><code>size</code></em> bytes in length. The result is identical to
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calling <code class="function">malloc</code>(<em class="parameter"><code></code></em>) with an argument of
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<em class="parameter"><code>number</code></em> * <em class="parameter"><code>size</code></em>, with the
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exception that the allocated memory is explicitly initialized to zero
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bytes.</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function
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allocates <em class="parameter"><code>size</code></em> bytes of memory such that the
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allocation's base address is a multiple of
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<em class="parameter"><code>alignment</code></em>, and returns the allocation in the value
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pointed to by <em class="parameter"><code>ptr</code></em>. The requested
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<em class="parameter"><code>alignment</code></em> must be a power of 2 at least as large as
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<code class="code">sizeof(<span class="type">void *</span>)</code>.</p><p>The <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function
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allocates <em class="parameter"><code>size</code></em> bytes of memory such that the
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allocation's base address is a multiple of
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<em class="parameter"><code>alignment</code></em>. The requested
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<em class="parameter"><code>alignment</code></em> must be a power of 2. Behavior is
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undefined if <em class="parameter"><code>size</code></em> is not an integral multiple of
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<em class="parameter"><code>alignment</code></em>.</p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function changes the
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size of the previously allocated memory referenced by
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<em class="parameter"><code>ptr</code></em> to <em class="parameter"><code>size</code></em> bytes. The
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contents of the memory are unchanged up to the lesser of the new and old
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sizes. If the new size is larger, the contents of the newly allocated
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portion of the memory are undefined. Upon success, the memory referenced
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by <em class="parameter"><code>ptr</code></em> is freed and a pointer to the newly
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allocated memory is returned. Note that
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<code class="function">realloc</code>(<em class="parameter"><code></code></em>) may move the memory allocation,
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resulting in a different return value than <em class="parameter"><code>ptr</code></em>.
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If <em class="parameter"><code>ptr</code></em> is <code class="constant">NULL</code>, the
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<code class="function">realloc</code>(<em class="parameter"><code></code></em>) function behaves identically to
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<code class="function">malloc</code>(<em class="parameter"><code></code></em>) for the specified size.</p><p>The <code class="function">free</code>(<em class="parameter"><code></code></em>) function causes the
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allocated memory referenced by <em class="parameter"><code>ptr</code></em> to be made
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available for future allocations. If <em class="parameter"><code>ptr</code></em> is
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<code class="constant">NULL</code>, no action occurs.</p></div><div class="refsect2"><a name="idp46144704"></a><h3>Non-standard API</h3><p>The <code class="function">mallocx</code>(<em class="parameter"><code></code></em>),
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<code class="function">rallocx</code>(<em class="parameter"><code></code></em>),
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<code class="function">xallocx</code>(<em class="parameter"><code></code></em>),
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<code class="function">sallocx</code>(<em class="parameter"><code></code></em>),
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<code class="function">dallocx</code>(<em class="parameter"><code></code></em>),
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<code class="function">sdallocx</code>(<em class="parameter"><code></code></em>), and
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<code class="function">nallocx</code>(<em class="parameter"><code></code></em>) functions all have a
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<em class="parameter"><code>flags</code></em> argument that can be used to specify
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options. The functions only check the options that are contextually
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relevant. Use bitwise or (<code class="code">|</code>) operations to
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specify one or more of the following:
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</p><div class="variablelist"><dl class="variablelist"><dt><a name="MALLOCX_LG_ALIGN"></a><span class="term"><code class="constant">MALLOCX_LG_ALIGN(<em class="parameter"><code>la</code></em>)
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</code></span></dt><dd><p>Align the memory allocation to start at an address
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that is a multiple of <code class="code">(1 <<
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<em class="parameter"><code>la</code></em>)</code>. This macro does not validate
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that <em class="parameter"><code>la</code></em> is within the valid
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range.</p></dd><dt><a name="MALLOCX_ALIGN"></a><span class="term"><code class="constant">MALLOCX_ALIGN(<em class="parameter"><code>a</code></em>)
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</code></span></dt><dd><p>Align the memory allocation to start at an address
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that is a multiple of <em class="parameter"><code>a</code></em>, where
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<em class="parameter"><code>a</code></em> is a power of two. This macro does not
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validate that <em class="parameter"><code>a</code></em> is a power of 2.
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</p></dd><dt><a name="MALLOCX_ZERO"></a><span class="term"><code class="constant">MALLOCX_ZERO</code></span></dt><dd><p>Initialize newly allocated memory to contain zero
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bytes. In the growing reallocation case, the real size prior to
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reallocation defines the boundary between untouched bytes and those
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that are initialized to contain zero bytes. If this macro is
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absent, newly allocated memory is uninitialized.</p></dd><dt><a name="MALLOCX_TCACHE"></a><span class="term"><code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)
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</code></span></dt><dd><p>Use the thread-specific cache (tcache) specified by
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the identifier <em class="parameter"><code>tc</code></em>, which must have been
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acquired via the <a class="link" href="#tcache.create">
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"<code class="mallctl">tcache.create</code>"
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</a>
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mallctl. This macro does not validate that
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<em class="parameter"><code>tc</code></em> specifies a valid
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identifier.</p></dd><dt><a name="MALLOC_TCACHE_NONE"></a><span class="term"><code class="constant">MALLOCX_TCACHE_NONE</code></span></dt><dd><p>Do not use a thread-specific cache (tcache). Unless
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<code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)</code> or
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<code class="constant">MALLOCX_TCACHE_NONE</code> is specified, an
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automatically managed tcache will be used under many circumstances.
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This macro cannot be used in the same <em class="parameter"><code>flags</code></em>
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argument as
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<code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)</code>.</p></dd><dt><a name="MALLOCX_ARENA"></a><span class="term"><code class="constant">MALLOCX_ARENA(<em class="parameter"><code>a</code></em>)
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</code></span></dt><dd><p>Use the arena specified by the index
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<em class="parameter"><code>a</code></em>. This macro has no effect for regions that
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were allocated via an arena other than the one specified. This
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macro does not validate that <em class="parameter"><code>a</code></em> specifies an
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arena index in the valid range.</p></dd></dl></div><p>
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</p><p>The <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function allocates at
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least <em class="parameter"><code>size</code></em> bytes of memory, and returns a pointer
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to the base address of the allocation. Behavior is undefined if
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<em class="parameter"><code>size</code></em> is <code class="constant">0</code>, or if request size
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overflows due to size class and/or alignment constraints.</p><p>The <code class="function">rallocx</code>(<em class="parameter"><code></code></em>) function resizes the
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allocation at <em class="parameter"><code>ptr</code></em> to be at least
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<em class="parameter"><code>size</code></em> bytes, and returns a pointer to the base
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address of the resulting allocation, which may or may not have moved from
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its original location. Behavior is undefined if
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<em class="parameter"><code>size</code></em> is <code class="constant">0</code>, or if request size
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overflows due to size class and/or alignment constraints.</p><p>The <code class="function">xallocx</code>(<em class="parameter"><code></code></em>) function resizes the
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allocation at <em class="parameter"><code>ptr</code></em> in place to be at least
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<em class="parameter"><code>size</code></em> bytes, and returns the real size of the
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allocation. If <em class="parameter"><code>extra</code></em> is non-zero, an attempt is
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made to resize the allocation to be at least <code class="code">(<em class="parameter"><code>size</code></em> +
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<em class="parameter"><code>extra</code></em>)</code> bytes, though inability to allocate
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the extra byte(s) will not by itself result in failure to resize.
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Behavior is undefined if <em class="parameter"><code>size</code></em> is
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<code class="constant">0</code>, or if <code class="code">(<em class="parameter"><code>size</code></em> + <em class="parameter"><code>extra</code></em>
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> <code class="constant">SIZE_T_MAX</code>)</code>.</p><p>The <code class="function">sallocx</code>(<em class="parameter"><code></code></em>) function returns the
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real size of the allocation at <em class="parameter"><code>ptr</code></em>.</p><p>The <code class="function">dallocx</code>(<em class="parameter"><code></code></em>) function causes the
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memory referenced by <em class="parameter"><code>ptr</code></em> to be made available for
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future allocations.</p><p>The <code class="function">sdallocx</code>(<em class="parameter"><code></code></em>) function is an
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extension of <code class="function">dallocx</code>(<em class="parameter"><code></code></em>) with a
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<em class="parameter"><code>size</code></em> parameter to allow the caller to pass in the
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allocation size as an optimization. The minimum valid input size is the
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original requested size of the allocation, and the maximum valid input
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size is the corresponding value returned by
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<code class="function">nallocx</code>(<em class="parameter"><code></code></em>) or
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<code class="function">sallocx</code>(<em class="parameter"><code></code></em>).</p><p>The <code class="function">nallocx</code>(<em class="parameter"><code></code></em>) function allocates no
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memory, but it performs the same size computation as the
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<code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function, and returns the real
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size of the allocation that would result from the equivalent
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<code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function call. Behavior is
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undefined if <em class="parameter"><code>size</code></em> is <code class="constant">0</code>, or if
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request size overflows due to size class and/or alignment
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constraints.</p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>) function provides a
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general interface for introspecting the memory allocator, as well as
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setting modifiable parameters and triggering actions. The
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period-separated <em class="parameter"><code>name</code></em> argument specifies a
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location in a tree-structured namespace; see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for
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documentation on the tree contents. To read a value, pass a pointer via
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<em class="parameter"><code>oldp</code></em> to adequate space to contain the value, and a
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pointer to its length via <em class="parameter"><code>oldlenp</code></em>; otherwise pass
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<code class="constant">NULL</code> and <code class="constant">NULL</code>. Similarly, to
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write a value, pass a pointer to the value via
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<em class="parameter"><code>newp</code></em>, and its length via
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<em class="parameter"><code>newlen</code></em>; otherwise pass <code class="constant">NULL</code>
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and <code class="constant">0</code>.</p><p>The <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>) function
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provides a way to avoid repeated name lookups for applications that
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repeatedly query the same portion of the namespace, by translating a name
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to a “Management Information Base” (MIB) that can be passed
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repeatedly to <code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>). Upon
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successful return from <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>),
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<em class="parameter"><code>mibp</code></em> contains an array of
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<em class="parameter"><code>*miblenp</code></em> integers, where
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<em class="parameter"><code>*miblenp</code></em> is the lesser of the number of components
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in <em class="parameter"><code>name</code></em> and the input value of
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<em class="parameter"><code>*miblenp</code></em>. Thus it is possible to pass a
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<em class="parameter"><code>*miblenp</code></em> that is smaller than the number of
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period-separated name components, which results in a partial MIB that can
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be used as the basis for constructing a complete MIB. For name
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components that are integers (e.g. the 2 in
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<a class="link" href="#arenas.bin.i.size">
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"<code class="mallctl">arenas.bin.2.size</code>"
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</a>),
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the corresponding MIB component will always be that integer. Therefore,
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it is legitimate to construct code like the following: </p><pre class="programlisting">
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unsigned nbins, i;
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size_t mib[4];
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size_t len, miblen;
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len = sizeof(nbins);
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mallctl("arenas.nbins", &nbins, &len, NULL, 0);
|
||
|
||
miblen = 4;
|
||
mallctlnametomib("arenas.bin.0.size", mib, &miblen);
|
||
for (i = 0; i < nbins; i++) {
|
||
size_t bin_size;
|
||
|
||
mib[2] = i;
|
||
len = sizeof(bin_size);
|
||
mallctlbymib(mib, miblen, &bin_size, &len, NULL, 0);
|
||
/* Do something with bin_size... */
|
||
}</pre><p>The <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>) function
|
||
writes human-readable summary statistics via the
|
||
<em class="parameter"><code>write_cb</code></em> callback function pointer and
|
||
<em class="parameter"><code>cbopaque</code></em> data passed to
|
||
<em class="parameter"><code>write_cb</code></em>, or
|
||
<code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) if
|
||
<em class="parameter"><code>write_cb</code></em> is <code class="constant">NULL</code>. This
|
||
function can be called repeatedly. General information that never
|
||
changes during execution can be omitted by specifying "g" as a character
|
||
within the <em class="parameter"><code>opts</code></em> string. Note that
|
||
<code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) uses the
|
||
<code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions internally, so
|
||
inconsistent statistics can be reported if multiple threads use these
|
||
functions simultaneously. If <code class="option">--enable-stats</code> is
|
||
specified during configuration, “m” and “a” can
|
||
be specified to omit merged arena and per arena statistics, respectively;
|
||
“b”, “l”, and “h” can be specified to
|
||
omit per size class statistics for bins, large objects, and huge objects,
|
||
respectively. Unrecognized characters are silently ignored. Note that
|
||
thread caching may prevent some statistics from being completely up to
|
||
date, since extra locking would be required to merge counters that track
|
||
thread cache operations.
|
||
</p><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function
|
||
returns the usable size of the allocation pointed to by
|
||
<em class="parameter"><code>ptr</code></em>. The return value may be larger than the size
|
||
that was requested during allocation. The
|
||
<code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function is not a
|
||
mechanism for in-place <code class="function">realloc</code>(<em class="parameter"><code></code></em>); rather
|
||
it is provided solely as a tool for introspection purposes. Any
|
||
discrepancy between the requested allocation size and the size reported
|
||
by <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) should not be
|
||
depended on, since such behavior is entirely implementation-dependent.
|
||
</p></div></div><div class="refsect1"><a name="tuning"></a><h2>TUNING</h2><p>Once, when the first call is made to one of the memory allocation
|
||
routines, the allocator initializes its internals based in part on various
|
||
options that can be specified at compile- or run-time.</p><p>The string pointed to by the global variable
|
||
<code class="varname">malloc_conf</code>, the “name” of the file
|
||
referenced by the symbolic link named <code class="filename">/etc/malloc.conf</code>, and the value of the
|
||
environment variable <code class="envar">MALLOC_CONF</code>, will be interpreted, in
|
||
that order, from left to right as options. Note that
|
||
<code class="varname">malloc_conf</code> may be read before
|
||
<code class="function">main</code>(<em class="parameter"><code></code></em>) is entered, so the declaration of
|
||
<code class="varname">malloc_conf</code> should specify an initializer that contains
|
||
the final value to be read by jemalloc. <code class="varname">malloc_conf</code> is
|
||
a compile-time setting, whereas <code class="filename">/etc/malloc.conf</code> and <code class="envar">MALLOC_CONF</code>
|
||
can be safely set any time prior to program invocation.</p><p>An options string is a comma-separated list of option:value pairs.
|
||
There is one key corresponding to each <a class="link" href="#opt.abort">
|
||
"<code class="mallctl">opt.*</code>"
|
||
</a> mallctl (see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for options
|
||
documentation). For example, <code class="literal">abort:true,narenas:1</code> sets
|
||
the <a class="link" href="#opt.abort">
|
||
"<code class="mallctl">opt.abort</code>"
|
||
</a> and <a class="link" href="#opt.narenas">
|
||
"<code class="mallctl">opt.narenas</code>"
|
||
</a> options. Some
|
||
options have boolean values (true/false), others have integer values (base
|
||
8, 10, or 16, depending on prefix), and yet others have raw string
|
||
values.</p></div><div class="refsect1"><a name="implementation_notes"></a><h2>IMPLEMENTATION NOTES</h2><p>Traditionally, allocators have used
|
||
<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> to obtain memory, which is
|
||
suboptimal for several reasons, including race conditions, increased
|
||
fragmentation, and artificial limitations on maximum usable memory. If
|
||
<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> is supported by the operating
|
||
system, this allocator uses both
|
||
<span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> and
|
||
<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>, in that order of preference;
|
||
otherwise only <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> is used.</p><p>This allocator uses multiple arenas in order to reduce lock
|
||
contention for threaded programs on multi-processor systems. This works
|
||
well with regard to threading scalability, but incurs some costs. There is
|
||
a small fixed per-arena overhead, and additionally, arenas manage memory
|
||
completely independently of each other, which means a small fixed increase
|
||
in overall memory fragmentation. These overheads are not generally an
|
||
issue, given the number of arenas normally used. Note that using
|
||
substantially more arenas than the default is not likely to improve
|
||
performance, mainly due to reduced cache performance. However, it may make
|
||
sense to reduce the number of arenas if an application does not make much
|
||
use of the allocation functions.</p><p>In addition to multiple arenas, unless
|
||
<code class="option">--disable-tcache</code> is specified during configuration, this
|
||
allocator supports thread-specific caching for small and large objects, in
|
||
order to make it possible to completely avoid synchronization for most
|
||
allocation requests. Such caching allows very fast allocation in the
|
||
common case, but it increases memory usage and fragmentation, since a
|
||
bounded number of objects can remain allocated in each thread cache.</p><p>Memory is conceptually broken into equal-sized chunks, where the
|
||
chunk size is a power of two that is greater than the page size. Chunks
|
||
are always aligned to multiples of the chunk size. This alignment makes it
|
||
possible to find metadata for user objects very quickly.</p><p>User objects are broken into three categories according to size:
|
||
small, large, and huge. Small and large objects are managed entirely by
|
||
arenas; huge objects are additionally aggregated in a single data structure
|
||
that is shared by all threads. Huge objects are typically used by
|
||
applications infrequently enough that this single data structure is not a
|
||
scalability issue.</p><p>Each chunk that is managed by an arena tracks its contents as runs of
|
||
contiguous pages (unused, backing a set of small objects, or backing one
|
||
large object). The combination of chunk alignment and chunk page maps
|
||
makes it possible to determine all metadata regarding small and large
|
||
allocations in constant time.</p><p>Small objects are managed in groups by page runs. Each run maintains
|
||
a bitmap to track which regions are in use. Allocation requests that are no
|
||
more than half the quantum (8 or 16, depending on architecture) are rounded
|
||
up to the nearest power of two that is at least <code class="code">sizeof(<span class="type">double</span>)</code>. All other object size
|
||
classes are multiples of the quantum, spaced such that there are four size
|
||
classes for each doubling in size, which limits internal fragmentation to
|
||
approximately 20% for all but the smallest size classes. Small size classes
|
||
are smaller than four times the page size, large size classes are smaller
|
||
than the chunk size (see the <a class="link" href="#opt.lg_chunk">
|
||
"<code class="mallctl">opt.lg_chunk</code>"
|
||
</a> option), and
|
||
huge size classes extend from the chunk size up to one size class less than
|
||
the full address space size.</p><p>Allocations are packed tightly together, which can be an issue for
|
||
multi-threaded applications. If you need to assure that allocations do not
|
||
suffer from cacheline sharing, round your allocation requests up to the
|
||
nearest multiple of the cacheline size, or specify cacheline alignment when
|
||
allocating.</p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>),
|
||
<code class="function">rallocx</code>(<em class="parameter"><code></code></em>), and
|
||
<code class="function">xallocx</code>(<em class="parameter"><code></code></em>) functions may resize allocations
|
||
without moving them under limited circumstances. Unlike the
|
||
<code class="function">*allocx</code>(<em class="parameter"><code></code></em>) API, the standard API does not
|
||
officially round up the usable size of an allocation to the nearest size
|
||
class, so technically it is necessary to call
|
||
<code class="function">realloc</code>(<em class="parameter"><code></code></em>) to grow e.g. a 9-byte allocation to
|
||
16 bytes, or shrink a 16-byte allocation to 9 bytes. Growth and shrinkage
|
||
trivially succeeds in place as long as the pre-size and post-size both round
|
||
up to the same size class. No other API guarantees are made regarding
|
||
in-place resizing, but the current implementation also tries to resize large
|
||
and huge allocations in place, as long as the pre-size and post-size are
|
||
both large or both huge. In such cases shrinkage always succeeds for large
|
||
size classes, but for huge size classes the chunk allocator must support
|
||
splitting (see <a class="link" href="#arena.i.chunk_hooks">
|
||
"<code class="mallctl">arena.<i>.chunk_hooks</code>"
|
||
</a>).
|
||
Growth only succeeds if the trailing memory is currently available, and
|
||
additionally for huge size classes the chunk allocator must support
|
||
merging.</p><p>Assuming 2 MiB chunks, 4 KiB pages, and a 16-byte quantum on a
|
||
64-bit system, the size classes in each category are as shown in <a class="xref" href="#size_classes" title="Table 1. Size classes">Table 1</a>.</p><div class="table"><a name="size_classes"></a><p class="title"><b>Table 1. Size classes</b></p><div class="table-contents"><table summary="Size classes" border="1"><colgroup><col align="left" class="c1"><col align="right" class="c2"><col align="left" class="c3"></colgroup><thead><tr><th align="left">Category</th><th align="right">Spacing</th><th align="left">Size</th></tr></thead><tbody><tr><td rowspan="9" align="left">Small</td><td align="right">lg</td><td align="left">[8]</td></tr><tr><td align="right">16</td><td align="left">[16, 32, 48, 64, 80, 96, 112, 128]</td></tr><tr><td align="right">32</td><td align="left">[160, 192, 224, 256]</td></tr><tr><td align="right">64</td><td align="left">[320, 384, 448, 512]</td></tr><tr><td align="right">128</td><td align="left">[640, 768, 896, 1024]</td></tr><tr><td align="right">256</td><td align="left">[1280, 1536, 1792, 2048]</td></tr><tr><td align="right">512</td><td align="left">[2560, 3072, 3584, 4096]</td></tr><tr><td align="right">1 KiB</td><td align="left">[5 KiB, 6 KiB, 7 KiB, 8 KiB]</td></tr><tr><td align="right">2 KiB</td><td align="left">[10 KiB, 12 KiB, 14 KiB]</td></tr><tr><td rowspan="8" align="left">Large</td><td align="right">2 KiB</td><td align="left">[16 KiB]</td></tr><tr><td align="right">4 KiB</td><td align="left">[20 KiB, 24 KiB, 28 KiB, 32 KiB]</td></tr><tr><td align="right">8 KiB</td><td align="left">[40 KiB, 48 KiB, 54 KiB, 64 KiB]</td></tr><tr><td align="right">16 KiB</td><td align="left">[80 KiB, 96 KiB, 112 KiB, 128 KiB]</td></tr><tr><td align="right">32 KiB</td><td align="left">[160 KiB, 192 KiB, 224 KiB, 256 KiB]</td></tr><tr><td align="right">64 KiB</td><td align="left">[320 KiB, 384 KiB, 448 KiB, 512 KiB]</td></tr><tr><td align="right">128 KiB</td><td align="left">[640 KiB, 768 KiB, 896 KiB, 1 MiB]</td></tr><tr><td align="right">256 KiB</td><td align="left">[1280 KiB, 1536 KiB, 1792 KiB]</td></tr><tr><td rowspan="7" align="left">Huge</td><td align="right">256 KiB</td><td align="left">[2 MiB]</td></tr><tr><td align="right">512 KiB</td><td align="left">[2560 KiB, 3 MiB, 3584 KiB, 4 MiB]</td></tr><tr><td align="right">1 MiB</td><td align="left">[5 MiB, 6 MiB, 7 MiB, 8 MiB]</td></tr><tr><td align="right">2 MiB</td><td align="left">[10 MiB, 12 MiB, 14 MiB, 16 MiB]</td></tr><tr><td align="right">4 MiB</td><td align="left">[20 MiB, 24 MiB, 28 MiB, 32 MiB]</td></tr><tr><td align="right">8 MiB</td><td align="left">[40 MiB, 48 MiB, 56 MiB, 64 MiB]</td></tr><tr><td align="right">...</td><td align="left">...</td></tr></tbody></table></div></div><br class="table-break"></div><div class="refsect1"><a name="mallctl_namespace"></a><h2>MALLCTL NAMESPACE</h2><p>The following names are defined in the namespace accessible via the
|
||
<code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions. Value types are
|
||
specified in parentheses, their readable/writable statuses are encoded as
|
||
<code class="literal">rw</code>, <code class="literal">r-</code>, <code class="literal">-w</code>, or
|
||
<code class="literal">--</code>, and required build configuration flags follow, if
|
||
any. A name element encoded as <code class="literal"><i></code> or
|
||
<code class="literal"><j></code> indicates an integer component, where the
|
||
integer varies from 0 to some upper value that must be determined via
|
||
introspection. In the case of
|
||
"<code class="mallctl">stats.arenas.<i>.*</code>"
|
||
,
|
||
<code class="literal"><i></code> equal to <a class="link" href="#arenas.narenas">
|
||
"<code class="mallctl">arenas.narenas</code>"
|
||
</a> can be
|
||
used to access the summation of statistics from all arenas. Take special
|
||
note of the <a class="link" href="#epoch">
|
||
"<code class="mallctl">epoch</code>"
|
||
</a> mallctl,
|
||
which controls refreshing of cached dynamic statistics.</p><div class="variablelist"><dl class="variablelist"><dt><a name="version"></a><span class="term">
|
||
|
||
"<code class="mallctl">version</code>"
|
||
|
||
(<span class="type">const char *</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Return the jemalloc version string.</p></dd><dt><a name="epoch"></a><span class="term">
|
||
|
||
"<code class="mallctl">epoch</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">rw</code>
|
||
</span></dt><dd><p>If a value is passed in, refresh the data from which
|
||
the <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions report values,
|
||
and increment the epoch. Return the current epoch. This is useful for
|
||
detecting whether another thread caused a refresh.</p></dd><dt><a name="config.cache_oblivious"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.cache_oblivious</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--enable-cache-oblivious</code> was specified
|
||
during build configuration.</p></dd><dt><a name="config.debug"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.debug</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--enable-debug</code> was specified during
|
||
build configuration.</p></dd><dt><a name="config.fill"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.fill</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--enable-fill</code> was specified during
|
||
build configuration.</p></dd><dt><a name="config.lazy_lock"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.lazy_lock</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--enable-lazy-lock</code> was specified
|
||
during build configuration.</p></dd><dt><a name="config.munmap"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.munmap</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--enable-munmap</code> was specified during
|
||
build configuration.</p></dd><dt><a name="config.prof"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.prof</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--enable-prof</code> was specified during
|
||
build configuration.</p></dd><dt><a name="config.prof_libgcc"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.prof_libgcc</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--disable-prof-libgcc</code> was not
|
||
specified during build configuration.</p></dd><dt><a name="config.prof_libunwind"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.prof_libunwind</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--enable-prof-libunwind</code> was specified
|
||
during build configuration.</p></dd><dt><a name="config.stats"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.stats</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--enable-stats</code> was specified during
|
||
build configuration.</p></dd><dt><a name="config.tcache"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.tcache</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--disable-tcache</code> was not specified
|
||
during build configuration.</p></dd><dt><a name="config.tls"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.tls</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--disable-tls</code> was not specified during
|
||
build configuration.</p></dd><dt><a name="config.utrace"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.utrace</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--enable-utrace</code> was specified during
|
||
build configuration.</p></dd><dt><a name="config.valgrind"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.valgrind</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--enable-valgrind</code> was specified during
|
||
build configuration.</p></dd><dt><a name="config.xmalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">config.xmalloc</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p><code class="option">--enable-xmalloc</code> was specified during
|
||
build configuration.</p></dd><dt><a name="opt.abort"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.abort</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Abort-on-warning enabled/disabled. If true, most
|
||
warnings are fatal. The process will call
|
||
<span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span> in these cases. This option is
|
||
disabled by default unless <code class="option">--enable-debug</code> is
|
||
specified during configuration, in which case it is enabled by default.
|
||
</p></dd><dt><a name="opt.dss"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.dss</code>"
|
||
|
||
(<span class="type">const char *</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>dss (<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>) allocation precedence as
|
||
related to <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> allocation. The following
|
||
settings are supported if
|
||
<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> is supported by the operating
|
||
system: “disabled”, “primary”, and
|
||
“secondary”; otherwise only “disabled” is
|
||
supported. The default is “secondary” if
|
||
<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> is supported by the operating
|
||
system; “disabled” otherwise.
|
||
</p></dd><dt><a name="opt.lg_chunk"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.lg_chunk</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Virtual memory chunk size (log base 2). If a chunk
|
||
size outside the supported size range is specified, the size is
|
||
silently clipped to the minimum/maximum supported size. The default
|
||
chunk size is 2 MiB (2^21).
|
||
</p></dd><dt><a name="opt.narenas"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.narenas</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Maximum number of arenas to use for automatic
|
||
multiplexing of threads and arenas. The default is four times the
|
||
number of CPUs, or one if there is a single CPU.</p></dd><dt><a name="opt.lg_dirty_mult"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.lg_dirty_mult</code>"
|
||
|
||
(<span class="type">ssize_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Per-arena minimum ratio (log base 2) of active to dirty
|
||
pages. Some dirty unused pages may be allowed to accumulate, within
|
||
the limit set by the ratio (or one chunk worth of dirty pages,
|
||
whichever is greater), before informing the kernel about some of those
|
||
pages via <span class="citerefentry"><span class="refentrytitle">madvise</span>(2)</span> or a similar system call. This
|
||
provides the kernel with sufficient information to recycle dirty pages
|
||
if physical memory becomes scarce and the pages remain unused. The
|
||
default minimum ratio is 8:1 (2^3:1); an option value of -1 will
|
||
disable dirty page purging. See <a class="link" href="#arenas.lg_dirty_mult">
|
||
"<code class="mallctl">arenas.lg_dirty_mult</code>"
|
||
</a>
|
||
and <a class="link" href="#arena.i.lg_dirty_mult">
|
||
"<code class="mallctl">arena.<i>.lg_dirty_mult</code>"
|
||
</a>
|
||
for related dynamic control options.</p></dd><dt><a name="opt.stats_print"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.stats_print</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Enable/disable statistics printing at exit. If
|
||
enabled, the <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>)
|
||
function is called at program exit via an
|
||
<span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function. If
|
||
<code class="option">--enable-stats</code> is specified during configuration, this
|
||
has the potential to cause deadlock for a multi-threaded process that
|
||
exits while one or more threads are executing in the memory allocation
|
||
functions. Furthermore, <code class="function">atexit</code>(<em class="parameter"><code></code></em>) may
|
||
allocate memory during application initialization and then deadlock
|
||
internally when jemalloc in turn calls
|
||
<code class="function">atexit</code>(<em class="parameter"><code></code></em>), so this option is not
|
||
univerally usable (though the application can register its own
|
||
<code class="function">atexit</code>(<em class="parameter"><code></code></em>) function with equivalent
|
||
functionality). Therefore, this option should only be used with care;
|
||
it is primarily intended as a performance tuning aid during application
|
||
development. This option is disabled by default.</p></dd><dt><a name="opt.junk"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.junk</code>"
|
||
|
||
(<span class="type">const char *</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-fill</code>]
|
||
</span></dt><dd><p>Junk filling. If set to "alloc", each byte of
|
||
uninitialized allocated memory will be initialized to
|
||
<code class="literal">0xa5</code>. If set to "free", all deallocated memory will
|
||
be initialized to <code class="literal">0x5a</code>. If set to "true", both
|
||
allocated and deallocated memory will be initialized, and if set to
|
||
"false", junk filling be disabled entirely. This is intended for
|
||
debugging and will impact performance negatively. This option is
|
||
"false" by default unless <code class="option">--enable-debug</code> is specified
|
||
during configuration, in which case it is "true" by default unless
|
||
running inside <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>.</p></dd><dt><a name="opt.quarantine"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.quarantine</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-fill</code>]
|
||
</span></dt><dd><p>Per thread quarantine size in bytes. If non-zero, each
|
||
thread maintains a FIFO object quarantine that stores up to the
|
||
specified number of bytes of memory. The quarantined memory is not
|
||
freed until it is released from quarantine, though it is immediately
|
||
junk-filled if the <a class="link" href="#opt.junk">
|
||
"<code class="mallctl">opt.junk</code>"
|
||
</a> option is
|
||
enabled. This feature is of particular use in combination with <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>, which can detect attempts
|
||
to access quarantined objects. This is intended for debugging and will
|
||
impact performance negatively. The default quarantine size is 0 unless
|
||
running inside Valgrind, in which case the default is 16
|
||
MiB.</p></dd><dt><a name="opt.redzone"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.redzone</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-fill</code>]
|
||
</span></dt><dd><p>Redzones enabled/disabled. If enabled, small
|
||
allocations have redzones before and after them. Furthermore, if the
|
||
<a class="link" href="#opt.junk">
|
||
"<code class="mallctl">opt.junk</code>"
|
||
</a> option is
|
||
enabled, the redzones are checked for corruption during deallocation.
|
||
However, the primary intended purpose of this feature is to be used in
|
||
combination with <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>,
|
||
which needs redzones in order to do effective buffer overflow/underflow
|
||
detection. This option is intended for debugging and will impact
|
||
performance negatively. This option is disabled by
|
||
default unless running inside Valgrind.</p></dd><dt><a name="opt.zero"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.zero</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-fill</code>]
|
||
</span></dt><dd><p>Zero filling enabled/disabled. If enabled, each byte
|
||
of uninitialized allocated memory will be initialized to 0. Note that
|
||
this initialization only happens once for each byte, so
|
||
<code class="function">realloc</code>(<em class="parameter"><code></code></em>) and
|
||
<code class="function">rallocx</code>(<em class="parameter"><code></code></em>) calls do not zero memory that
|
||
was previously allocated. This is intended for debugging and will
|
||
impact performance negatively. This option is disabled by default.
|
||
</p></dd><dt><a name="opt.utrace"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.utrace</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-utrace</code>]
|
||
</span></dt><dd><p>Allocation tracing based on
|
||
<span class="citerefentry"><span class="refentrytitle">utrace</span>(2)</span> enabled/disabled. This option
|
||
is disabled by default.</p></dd><dt><a name="opt.xmalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.xmalloc</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-xmalloc</code>]
|
||
</span></dt><dd><p>Abort-on-out-of-memory enabled/disabled. If enabled,
|
||
rather than returning failure for any allocation function, display a
|
||
diagnostic message on <code class="constant">STDERR_FILENO</code> and cause the
|
||
program to drop core (using
|
||
<span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span>). If an application is
|
||
designed to depend on this behavior, set the option at compile time by
|
||
including the following in the source code:
|
||
</p><pre class="programlisting">
|
||
malloc_conf = "xmalloc:true";</pre><p>
|
||
This option is disabled by default.</p></dd><dt><a name="opt.tcache"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.tcache</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-tcache</code>]
|
||
</span></dt><dd><p>Thread-specific caching (tcache) enabled/disabled. When
|
||
there are multiple threads, each thread uses a tcache for objects up to
|
||
a certain size. Thread-specific caching allows many allocations to be
|
||
satisfied without performing any thread synchronization, at the cost of
|
||
increased memory use. See the <a class="link" href="#opt.lg_tcache_max">
|
||
"<code class="mallctl">opt.lg_tcache_max</code>"
|
||
</a>
|
||
option for related tuning information. This option is enabled by
|
||
default unless running inside <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>, in which case it is
|
||
forcefully disabled.</p></dd><dt><a name="opt.lg_tcache_max"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.lg_tcache_max</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-tcache</code>]
|
||
</span></dt><dd><p>Maximum size class (log base 2) to cache in the
|
||
thread-specific cache (tcache). At a minimum, all small size classes
|
||
are cached, and at a maximum all large size classes are cached. The
|
||
default maximum is 32 KiB (2^15).</p></dd><dt><a name="opt.prof"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.prof</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Memory profiling enabled/disabled. If enabled, profile
|
||
memory allocation activity. See the <a class="link" href="#opt.prof_active">
|
||
"<code class="mallctl">opt.prof_active</code>"
|
||
</a>
|
||
option for on-the-fly activation/deactivation. See the <a class="link" href="#opt.lg_prof_sample">
|
||
"<code class="mallctl">opt.lg_prof_sample</code>"
|
||
</a>
|
||
option for probabilistic sampling control. See the <a class="link" href="#opt.prof_accum">
|
||
"<code class="mallctl">opt.prof_accum</code>"
|
||
</a>
|
||
option for control of cumulative sample reporting. See the <a class="link" href="#opt.lg_prof_interval">
|
||
"<code class="mallctl">opt.lg_prof_interval</code>"
|
||
</a>
|
||
option for information on interval-triggered profile dumping, the <a class="link" href="#opt.prof_gdump">
|
||
"<code class="mallctl">opt.prof_gdump</code>"
|
||
</a>
|
||
option for information on high-water-triggered profile dumping, and the
|
||
<a class="link" href="#opt.prof_final">
|
||
"<code class="mallctl">opt.prof_final</code>"
|
||
</a>
|
||
option for final profile dumping. Profile output is compatible with
|
||
the <span class="command"><strong>jeprof</strong></span> command, which is based on the
|
||
<span class="command"><strong>pprof</strong></span> that is developed as part of the <a class="ulink" href="http://code.google.com/p/gperftools/" target="_top">gperftools
|
||
package</a>.</p></dd><dt><a name="opt.prof_prefix"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.prof_prefix</code>"
|
||
|
||
(<span class="type">const char *</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Filename prefix for profile dumps. If the prefix is
|
||
set to the empty string, no automatic dumps will occur; this is
|
||
primarily useful for disabling the automatic final heap dump (which
|
||
also disables leak reporting, if enabled). The default prefix is
|
||
<code class="filename">jeprof</code>.</p></dd><dt><a name="opt.prof_active"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.prof_active</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Profiling activated/deactivated. This is a secondary
|
||
control mechanism that makes it possible to start the application with
|
||
profiling enabled (see the <a class="link" href="#opt.prof">
|
||
"<code class="mallctl">opt.prof</code>"
|
||
</a> option) but
|
||
inactive, then toggle profiling at any time during program execution
|
||
with the <a class="link" href="#prof.active">
|
||
"<code class="mallctl">prof.active</code>"
|
||
</a> mallctl.
|
||
This option is enabled by default.</p></dd><dt><a name="opt.prof_thread_active_init"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.prof_thread_active_init</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Initial setting for <a class="link" href="#thread.prof.active">
|
||
"<code class="mallctl">thread.prof.active</code>"
|
||
</a>
|
||
in newly created threads. The initial setting for newly created threads
|
||
can also be changed during execution via the <a class="link" href="#prof.thread_active_init">
|
||
"<code class="mallctl">prof.thread_active_init</code>"
|
||
</a>
|
||
mallctl. This option is enabled by default.</p></dd><dt><a name="opt.lg_prof_sample"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.lg_prof_sample</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Average interval (log base 2) between allocation
|
||
samples, as measured in bytes of allocation activity. Increasing the
|
||
sampling interval decreases profile fidelity, but also decreases the
|
||
computational overhead. The default sample interval is 512 KiB (2^19
|
||
B).</p></dd><dt><a name="opt.prof_accum"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.prof_accum</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Reporting of cumulative object/byte counts in profile
|
||
dumps enabled/disabled. If this option is enabled, every unique
|
||
backtrace must be stored for the duration of execution. Depending on
|
||
the application, this can impose a large memory overhead, and the
|
||
cumulative counts are not always of interest. This option is disabled
|
||
by default.</p></dd><dt><a name="opt.lg_prof_interval"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.lg_prof_interval</code>"
|
||
|
||
(<span class="type">ssize_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Average interval (log base 2) between memory profile
|
||
dumps, as measured in bytes of allocation activity. The actual
|
||
interval between dumps may be sporadic because decentralized allocation
|
||
counters are used to avoid synchronization bottlenecks. Profiles are
|
||
dumped to files named according to the pattern
|
||
<code class="filename"><prefix>.<pid>.<seq>.i<iseq>.heap</code>,
|
||
where <code class="literal"><prefix></code> is controlled by the
|
||
<a class="link" href="#opt.prof_prefix">
|
||
"<code class="mallctl">opt.prof_prefix</code>"
|
||
</a>
|
||
option. By default, interval-triggered profile dumping is disabled
|
||
(encoded as -1).
|
||
</p></dd><dt><a name="opt.prof_gdump"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.prof_gdump</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Set the initial state of <a class="link" href="#prof.gdump">
|
||
"<code class="mallctl">prof.gdump</code>"
|
||
</a>, which when
|
||
enabled triggers a memory profile dump every time the total virtual
|
||
memory exceeds the previous maximum. This option is disabled by
|
||
default.</p></dd><dt><a name="opt.prof_final"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.prof_final</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Use an
|
||
<span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to dump final memory
|
||
usage to a file named according to the pattern
|
||
<code class="filename"><prefix>.<pid>.<seq>.f.heap</code>,
|
||
where <code class="literal"><prefix></code> is controlled by the <a class="link" href="#opt.prof_prefix">
|
||
"<code class="mallctl">opt.prof_prefix</code>"
|
||
</a>
|
||
option. Note that <code class="function">atexit</code>(<em class="parameter"><code></code></em>) may allocate
|
||
memory during application initialization and then deadlock internally
|
||
when jemalloc in turn calls <code class="function">atexit</code>(<em class="parameter"><code></code></em>), so
|
||
this option is not univerally usable (though the application can
|
||
register its own <code class="function">atexit</code>(<em class="parameter"><code></code></em>) function with
|
||
equivalent functionality). This option is disabled by
|
||
default.</p></dd><dt><a name="opt.prof_leak"></a><span class="term">
|
||
|
||
"<code class="mallctl">opt.prof_leak</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Leak reporting enabled/disabled. If enabled, use an
|
||
<span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to report memory leaks
|
||
detected by allocation sampling. See the
|
||
<a class="link" href="#opt.prof">
|
||
"<code class="mallctl">opt.prof</code>"
|
||
</a> option for
|
||
information on analyzing heap profile output. This option is disabled
|
||
by default.</p></dd><dt><a name="thread.arena"></a><span class="term">
|
||
|
||
"<code class="mallctl">thread.arena</code>"
|
||
|
||
(<span class="type">unsigned</span>)
|
||
<code class="literal">rw</code>
|
||
</span></dt><dd><p>Get or set the arena associated with the calling
|
||
thread. If the specified arena was not initialized beforehand (see the
|
||
<a class="link" href="#arenas.initialized">
|
||
"<code class="mallctl">arenas.initialized</code>"
|
||
</a>
|
||
mallctl), it will be automatically initialized as a side effect of
|
||
calling this interface.</p></dd><dt><a name="thread.allocated"></a><span class="term">
|
||
|
||
"<code class="mallctl">thread.allocated</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Get the total number of bytes ever allocated by the
|
||
calling thread. This counter has the potential to wrap around; it is
|
||
up to the application to appropriately interpret the counter in such
|
||
cases.</p></dd><dt><a name="thread.allocatedp"></a><span class="term">
|
||
|
||
"<code class="mallctl">thread.allocatedp</code>"
|
||
|
||
(<span class="type">uint64_t *</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Get a pointer to the the value that is returned by the
|
||
<a class="link" href="#thread.allocated">
|
||
"<code class="mallctl">thread.allocated</code>"
|
||
</a>
|
||
mallctl. This is useful for avoiding the overhead of repeated
|
||
<code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><a name="thread.deallocated"></a><span class="term">
|
||
|
||
"<code class="mallctl">thread.deallocated</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Get the total number of bytes ever deallocated by the
|
||
calling thread. This counter has the potential to wrap around; it is
|
||
up to the application to appropriately interpret the counter in such
|
||
cases.</p></dd><dt><a name="thread.deallocatedp"></a><span class="term">
|
||
|
||
"<code class="mallctl">thread.deallocatedp</code>"
|
||
|
||
(<span class="type">uint64_t *</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Get a pointer to the the value that is returned by the
|
||
<a class="link" href="#thread.deallocated">
|
||
"<code class="mallctl">thread.deallocated</code>"
|
||
</a>
|
||
mallctl. This is useful for avoiding the overhead of repeated
|
||
<code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><a name="thread.tcache.enabled"></a><span class="term">
|
||
|
||
"<code class="mallctl">thread.tcache.enabled</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">rw</code>
|
||
[<code class="option">--enable-tcache</code>]
|
||
</span></dt><dd><p>Enable/disable calling thread's tcache. The tcache is
|
||
implicitly flushed as a side effect of becoming
|
||
disabled (see <a class="link" href="#thread.tcache.flush">
|
||
"<code class="mallctl">thread.tcache.flush</code>"
|
||
</a>).
|
||
</p></dd><dt><a name="thread.tcache.flush"></a><span class="term">
|
||
|
||
"<code class="mallctl">thread.tcache.flush</code>"
|
||
|
||
(<span class="type">void</span>)
|
||
<code class="literal">--</code>
|
||
[<code class="option">--enable-tcache</code>]
|
||
</span></dt><dd><p>Flush calling thread's thread-specific cache (tcache).
|
||
This interface releases all cached objects and internal data structures
|
||
associated with the calling thread's tcache. Ordinarily, this interface
|
||
need not be called, since automatic periodic incremental garbage
|
||
collection occurs, and the thread cache is automatically discarded when
|
||
a thread exits. However, garbage collection is triggered by allocation
|
||
activity, so it is possible for a thread that stops
|
||
allocating/deallocating to retain its cache indefinitely, in which case
|
||
the developer may find manual flushing useful.</p></dd><dt><a name="thread.prof.name"></a><span class="term">
|
||
|
||
"<code class="mallctl">thread.prof.name</code>"
|
||
|
||
(<span class="type">const char *</span>)
|
||
<code class="literal">r-</code> or
|
||
<code class="literal">-w</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Get/set the descriptive name associated with the calling
|
||
thread in memory profile dumps. An internal copy of the name string is
|
||
created, so the input string need not be maintained after this interface
|
||
completes execution. The output string of this interface should be
|
||
copied for non-ephemeral uses, because multiple implementation details
|
||
can cause asynchronous string deallocation. Furthermore, each
|
||
invocation of this interface can only read or write; simultaneous
|
||
read/write is not supported due to string lifetime limitations. The
|
||
name string must nil-terminated and comprised only of characters in the
|
||
sets recognized
|
||
by <span class="citerefentry"><span class="refentrytitle">isgraph</span>(3)</span> and
|
||
<span class="citerefentry"><span class="refentrytitle">isblank</span>(3)</span>.</p></dd><dt><a name="thread.prof.active"></a><span class="term">
|
||
|
||
"<code class="mallctl">thread.prof.active</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">rw</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Control whether sampling is currently active for the
|
||
calling thread. This is an activation mechanism in addition to <a class="link" href="#prof.active">
|
||
"<code class="mallctl">prof.active</code>"
|
||
</a>; both must
|
||
be active for the calling thread to sample. This flag is enabled by
|
||
default.</p></dd><dt><a name="tcache.create"></a><span class="term">
|
||
|
||
"<code class="mallctl">tcache.create</code>"
|
||
|
||
(<span class="type">unsigned</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-tcache</code>]
|
||
</span></dt><dd><p>Create an explicit thread-specific cache (tcache) and
|
||
return an identifier that can be passed to the <a class="link" href="#MALLOCX_TCACHE"><code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)</code></a>
|
||
macro to explicitly use the specified cache rather than the
|
||
automatically managed one that is used by default. Each explicit cache
|
||
can be used by only one thread at a time; the application must assure
|
||
that this constraint holds.
|
||
</p></dd><dt><a name="tcache.flush"></a><span class="term">
|
||
|
||
"<code class="mallctl">tcache.flush</code>"
|
||
|
||
(<span class="type">unsigned</span>)
|
||
<code class="literal">-w</code>
|
||
[<code class="option">--enable-tcache</code>]
|
||
</span></dt><dd><p>Flush the specified thread-specific cache (tcache). The
|
||
same considerations apply to this interface as to <a class="link" href="#thread.tcache.flush">
|
||
"<code class="mallctl">thread.tcache.flush</code>"
|
||
</a>,
|
||
except that the tcache will never be automatically be discarded.
|
||
</p></dd><dt><a name="tcache.destroy"></a><span class="term">
|
||
|
||
"<code class="mallctl">tcache.destroy</code>"
|
||
|
||
(<span class="type">unsigned</span>)
|
||
<code class="literal">-w</code>
|
||
[<code class="option">--enable-tcache</code>]
|
||
</span></dt><dd><p>Flush the specified thread-specific cache (tcache) and
|
||
make the identifier available for use during a future tcache creation.
|
||
</p></dd><dt><a name="arena.i.purge"></a><span class="term">
|
||
|
||
"<code class="mallctl">arena.<i>.purge</code>"
|
||
|
||
(<span class="type">void</span>)
|
||
<code class="literal">--</code>
|
||
</span></dt><dd><p>Purge unused dirty pages for arena <i>, or for
|
||
all arenas if <i> equals <a class="link" href="#arenas.narenas">
|
||
"<code class="mallctl">arenas.narenas</code>"
|
||
</a>.
|
||
</p></dd><dt><a name="arena.i.dss"></a><span class="term">
|
||
|
||
"<code class="mallctl">arena.<i>.dss</code>"
|
||
|
||
(<span class="type">const char *</span>)
|
||
<code class="literal">rw</code>
|
||
</span></dt><dd><p>Set the precedence of dss allocation as related to mmap
|
||
allocation for arena <i>, or for all arenas if <i> equals
|
||
<a class="link" href="#arenas.narenas">
|
||
"<code class="mallctl">arenas.narenas</code>"
|
||
</a>. See
|
||
<a class="link" href="#opt.dss">
|
||
"<code class="mallctl">opt.dss</code>"
|
||
</a> for supported
|
||
settings.</p></dd><dt><a name="arena.i.lg_dirty_mult"></a><span class="term">
|
||
|
||
"<code class="mallctl">arena.<i>.lg_dirty_mult</code>"
|
||
|
||
(<span class="type">ssize_t</span>)
|
||
<code class="literal">rw</code>
|
||
</span></dt><dd><p>Current per-arena minimum ratio (log base 2) of active
|
||
to dirty pages for arena <i>. Each time this interface is set and
|
||
the ratio is increased, pages are synchronously purged as necessary to
|
||
impose the new ratio. See <a class="link" href="#opt.lg_dirty_mult">
|
||
"<code class="mallctl">opt.lg_dirty_mult</code>"
|
||
</a>
|
||
for additional information.</p></dd><dt><a name="arena.i.chunk_hooks"></a><span class="term">
|
||
|
||
"<code class="mallctl">arena.<i>.chunk_hooks</code>"
|
||
|
||
(<span class="type">chunk_hooks_t</span>)
|
||
<code class="literal">rw</code>
|
||
</span></dt><dd><p>Get or set the chunk management hook functions for arena
|
||
<i>. The functions must be capable of operating on all extant
|
||
chunks associated with arena <i>, usually by passing unknown
|
||
chunks to the replaced functions. In practice, it is feasible to
|
||
control allocation for arenas created via <a class="link" href="#arenas.extend">
|
||
"<code class="mallctl">arenas.extend</code>"
|
||
</a> such
|
||
that all chunks originate from an application-supplied chunk allocator
|
||
(by setting custom chunk hook functions just after arena creation), but
|
||
the automatically created arenas may have already created chunks prior
|
||
to the application having an opportunity to take over chunk
|
||
allocation.</p><pre class="programlisting">
|
||
typedef struct {
|
||
chunk_alloc_t *alloc;
|
||
chunk_dalloc_t *dalloc;
|
||
chunk_commit_t *commit;
|
||
chunk_decommit_t *decommit;
|
||
chunk_purge_t *purge;
|
||
chunk_split_t *split;
|
||
chunk_merge_t *merge;
|
||
} chunk_hooks_t;</pre><p>The <span class="type">chunk_hooks_t</span> structure comprises function
|
||
pointers which are described individually below. jemalloc uses these
|
||
functions to manage chunk lifetime, which starts off with allocation of
|
||
mapped committed memory, in the simplest case followed by deallocation.
|
||
However, there are performance and platform reasons to retain chunks for
|
||
later reuse. Cleanup attempts cascade from deallocation to decommit to
|
||
purging, which gives the chunk management functions opportunities to
|
||
reject the most permanent cleanup operations in favor of less permanent
|
||
(and often less costly) operations. The chunk splitting and merging
|
||
operations can also be opted out of, but this is mainly intended to
|
||
support platforms on which virtual memory mappings provided by the
|
||
operating system kernel do not automatically coalesce and split, e.g.
|
||
Windows.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef void *<b class="fsfunc">(chunk_alloc_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>bool *<var class="pdparam">zero</var>, </td></tr><tr><td> </td><td>bool *<var class="pdparam">commit</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk allocation function conforms to the
|
||
<span class="type">chunk_alloc_t</span> type and upon success returns a pointer to
|
||
<em class="parameter"><code>size</code></em> bytes of mapped memory on behalf of arena
|
||
<em class="parameter"><code>arena_ind</code></em> such that the chunk's base address is a
|
||
multiple of <em class="parameter"><code>alignment</code></em>, as well as setting
|
||
<em class="parameter"><code>*zero</code></em> to indicate whether the chunk is zeroed and
|
||
<em class="parameter"><code>*commit</code></em> to indicate whether the chunk is
|
||
committed. Upon error the function returns <code class="constant">NULL</code>
|
||
and leaves <em class="parameter"><code>*zero</code></em> and
|
||
<em class="parameter"><code>*commit</code></em> unmodified. The
|
||
<em class="parameter"><code>size</code></em> parameter is always a multiple of the chunk
|
||
size. The <em class="parameter"><code>alignment</code></em> parameter is always a power
|
||
of two at least as large as the chunk size. Zeroing is mandatory if
|
||
<em class="parameter"><code>*zero</code></em> is true upon function entry. Committing is
|
||
mandatory if <em class="parameter"><code>*commit</code></em> is true upon function entry.
|
||
If <em class="parameter"><code>chunk</code></em> is not <code class="constant">NULL</code>, the
|
||
returned pointer must be <em class="parameter"><code>chunk</code></em> on success or
|
||
<code class="constant">NULL</code> on error. Committed memory may be committed
|
||
in absolute terms as on a system that does not overcommit, or in
|
||
implicit terms as on a system that overcommits and satisfies physical
|
||
memory needs on demand via soft page faults. Note that replacing the
|
||
default chunk allocation function makes the arena's <a class="link" href="#arena.i.dss">
|
||
"<code class="mallctl">arena.<i>.dss</code>"
|
||
</a>
|
||
setting irrelevant.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_dalloc_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>bool <var class="pdparam">committed</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>
|
||
A chunk deallocation function conforms to the
|
||
<span class="type">chunk_dalloc_t</span> type and deallocates a
|
||
<em class="parameter"><code>chunk</code></em> of given <em class="parameter"><code>size</code></em> with
|
||
<em class="parameter"><code>committed</code></em>/decommited memory as indicated, on
|
||
behalf of arena <em class="parameter"><code>arena_ind</code></em>, returning false upon
|
||
success. If the function returns true, this indicates opt-out from
|
||
deallocation; the virtual memory mapping associated with the chunk
|
||
remains mapped, in the same commit state, and available for future use,
|
||
in which case it will be automatically retained for later reuse.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_commit_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">offset</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk commit function conforms to the
|
||
<span class="type">chunk_commit_t</span> type and commits zeroed physical memory to
|
||
back pages within a <em class="parameter"><code>chunk</code></em> of given
|
||
<em class="parameter"><code>size</code></em> at <em class="parameter"><code>offset</code></em> bytes,
|
||
extending for <em class="parameter"><code>length</code></em> on behalf of arena
|
||
<em class="parameter"><code>arena_ind</code></em>, returning false upon success.
|
||
Committed memory may be committed in absolute terms as on a system that
|
||
does not overcommit, or in implicit terms as on a system that
|
||
overcommits and satisfies physical memory needs on demand via soft page
|
||
faults. If the function returns true, this indicates insufficient
|
||
physical memory to satisfy the request.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_decommit_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">offset</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk decommit function conforms to the
|
||
<span class="type">chunk_decommit_t</span> type and decommits any physical memory
|
||
that is backing pages within a <em class="parameter"><code>chunk</code></em> of given
|
||
<em class="parameter"><code>size</code></em> at <em class="parameter"><code>offset</code></em> bytes,
|
||
extending for <em class="parameter"><code>length</code></em> on behalf of arena
|
||
<em class="parameter"><code>arena_ind</code></em>, returning false upon success, in which
|
||
case the pages will be committed via the chunk commit function before
|
||
being reused. If the function returns true, this indicates opt-out from
|
||
decommit; the memory remains committed and available for future use, in
|
||
which case it will be automatically retained for later reuse.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_purge_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t<var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">offset</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk purge function conforms to the <span class="type">chunk_purge_t</span>
|
||
type and optionally discards physical pages within the virtual memory
|
||
mapping associated with <em class="parameter"><code>chunk</code></em> of given
|
||
<em class="parameter"><code>size</code></em> at <em class="parameter"><code>offset</code></em> bytes,
|
||
extending for <em class="parameter"><code>length</code></em> on behalf of arena
|
||
<em class="parameter"><code>arena_ind</code></em>, returning false if pages within the
|
||
purged virtual memory range will be zero-filled the next time they are
|
||
accessed.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_split_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_a</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_b</var>, </td></tr><tr><td> </td><td>bool <var class="pdparam">committed</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk split function conforms to the <span class="type">chunk_split_t</span>
|
||
type and optionally splits <em class="parameter"><code>chunk</code></em> of given
|
||
<em class="parameter"><code>size</code></em> into two adjacent chunks, the first of
|
||
<em class="parameter"><code>size_a</code></em> bytes, and the second of
|
||
<em class="parameter"><code>size_b</code></em> bytes, operating on
|
||
<em class="parameter"><code>committed</code></em>/decommitted memory as indicated, on
|
||
behalf of arena <em class="parameter"><code>arena_ind</code></em>, returning false upon
|
||
success. If the function returns true, this indicates that the chunk
|
||
remains unsplit and therefore should continue to be operated on as a
|
||
whole.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_merge_t)</b>(</code></td><td>void *<var class="pdparam">chunk_a</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_a</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">chunk_b</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_b</var>, </td></tr><tr><td> </td><td>bool <var class="pdparam">committed</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk merge function conforms to the <span class="type">chunk_merge_t</span>
|
||
type and optionally merges adjacent chunks,
|
||
<em class="parameter"><code>chunk_a</code></em> of given <em class="parameter"><code>size_a</code></em>
|
||
and <em class="parameter"><code>chunk_b</code></em> of given
|
||
<em class="parameter"><code>size_b</code></em> into one contiguous chunk, operating on
|
||
<em class="parameter"><code>committed</code></em>/decommitted memory as indicated, on
|
||
behalf of arena <em class="parameter"><code>arena_ind</code></em>, returning false upon
|
||
success. If the function returns true, this indicates that the chunks
|
||
remain distinct mappings and therefore should continue to be operated on
|
||
independently.</p></dd><dt><a name="arenas.narenas"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.narenas</code>"
|
||
|
||
(<span class="type">unsigned</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Current limit on number of arenas.</p></dd><dt><a name="arenas.initialized"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.initialized</code>"
|
||
|
||
(<span class="type">bool *</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>An array of <a class="link" href="#arenas.narenas">
|
||
"<code class="mallctl">arenas.narenas</code>"
|
||
</a>
|
||
booleans. Each boolean indicates whether the corresponding arena is
|
||
initialized.</p></dd><dt><a name="arenas.lg_dirty_mult"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.lg_dirty_mult</code>"
|
||
|
||
(<span class="type">ssize_t</span>)
|
||
<code class="literal">rw</code>
|
||
</span></dt><dd><p>Current default per-arena minimum ratio (log base 2) of
|
||
active to dirty pages, used to initialize <a class="link" href="#arena.i.lg_dirty_mult">
|
||
"<code class="mallctl">arena.<i>.lg_dirty_mult</code>"
|
||
</a>
|
||
during arena creation. See <a class="link" href="#opt.lg_dirty_mult">
|
||
"<code class="mallctl">opt.lg_dirty_mult</code>"
|
||
</a>
|
||
for additional information.</p></dd><dt><a name="arenas.quantum"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.quantum</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Quantum size.</p></dd><dt><a name="arenas.page"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.page</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Page size.</p></dd><dt><a name="arenas.tcache_max"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.tcache_max</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-tcache</code>]
|
||
</span></dt><dd><p>Maximum thread-cached size class.</p></dd><dt><a name="arenas.nbins"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.nbins</code>"
|
||
|
||
(<span class="type">unsigned</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Number of bin size classes.</p></dd><dt><a name="arenas.nhbins"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.nhbins</code>"
|
||
|
||
(<span class="type">unsigned</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-tcache</code>]
|
||
</span></dt><dd><p>Total number of thread cache bin size
|
||
classes.</p></dd><dt><a name="arenas.bin.i.size"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.bin.<i>.size</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Maximum size supported by size class.</p></dd><dt><a name="arenas.bin.i.nregs"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.bin.<i>.nregs</code>"
|
||
|
||
(<span class="type">uint32_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Number of regions per page run.</p></dd><dt><a name="arenas.bin.i.run_size"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.bin.<i>.run_size</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Number of bytes per page run.</p></dd><dt><a name="arenas.nlruns"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.nlruns</code>"
|
||
|
||
(<span class="type">unsigned</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Total number of large size classes.</p></dd><dt><a name="arenas.lrun.i.size"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.lrun.<i>.size</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Maximum size supported by this large size
|
||
class.</p></dd><dt><a name="arenas.nhchunks"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.nhchunks</code>"
|
||
|
||
(<span class="type">unsigned</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Total number of huge size classes.</p></dd><dt><a name="arenas.hchunk.i.size"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.hchunk.<i>.size</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Maximum size supported by this huge size
|
||
class.</p></dd><dt><a name="arenas.extend"></a><span class="term">
|
||
|
||
"<code class="mallctl">arenas.extend</code>"
|
||
|
||
(<span class="type">unsigned</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Extend the array of arenas by appending a new arena,
|
||
and returning the new arena index.</p></dd><dt><a name="prof.thread_active_init"></a><span class="term">
|
||
|
||
"<code class="mallctl">prof.thread_active_init</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">rw</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Control the initial setting for <a class="link" href="#thread.prof.active">
|
||
"<code class="mallctl">thread.prof.active</code>"
|
||
</a>
|
||
in newly created threads. See the <a class="link" href="#opt.prof_thread_active_init">
|
||
"<code class="mallctl">opt.prof_thread_active_init</code>"
|
||
</a>
|
||
option for additional information.</p></dd><dt><a name="prof.active"></a><span class="term">
|
||
|
||
"<code class="mallctl">prof.active</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">rw</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Control whether sampling is currently active. See the
|
||
<a class="link" href="#opt.prof_active">
|
||
"<code class="mallctl">opt.prof_active</code>"
|
||
</a>
|
||
option for additional information, as well as the interrelated <a class="link" href="#thread.prof.active">
|
||
"<code class="mallctl">thread.prof.active</code>"
|
||
</a>
|
||
mallctl.</p></dd><dt><a name="prof.dump"></a><span class="term">
|
||
|
||
"<code class="mallctl">prof.dump</code>"
|
||
|
||
(<span class="type">const char *</span>)
|
||
<code class="literal">-w</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Dump a memory profile to the specified file, or if NULL
|
||
is specified, to a file according to the pattern
|
||
<code class="filename"><prefix>.<pid>.<seq>.m<mseq>.heap</code>,
|
||
where <code class="literal"><prefix></code> is controlled by the
|
||
<a class="link" href="#opt.prof_prefix">
|
||
"<code class="mallctl">opt.prof_prefix</code>"
|
||
</a>
|
||
option.</p></dd><dt><a name="prof.gdump"></a><span class="term">
|
||
|
||
"<code class="mallctl">prof.gdump</code>"
|
||
|
||
(<span class="type">bool</span>)
|
||
<code class="literal">rw</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>When enabled, trigger a memory profile dump every time
|
||
the total virtual memory exceeds the previous maximum. Profiles are
|
||
dumped to files named according to the pattern
|
||
<code class="filename"><prefix>.<pid>.<seq>.u<useq>.heap</code>,
|
||
where <code class="literal"><prefix></code> is controlled by the <a class="link" href="#opt.prof_prefix">
|
||
"<code class="mallctl">opt.prof_prefix</code>"
|
||
</a>
|
||
option.</p></dd><dt><a name="prof.reset"></a><span class="term">
|
||
|
||
"<code class="mallctl">prof.reset</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">-w</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Reset all memory profile statistics, and optionally
|
||
update the sample rate (see <a class="link" href="#opt.lg_prof_sample">
|
||
"<code class="mallctl">opt.lg_prof_sample</code>"
|
||
</a>
|
||
and <a class="link" href="#prof.lg_sample">
|
||
"<code class="mallctl">prof.lg_sample</code>"
|
||
</a>).
|
||
</p></dd><dt><a name="prof.lg_sample"></a><span class="term">
|
||
|
||
"<code class="mallctl">prof.lg_sample</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Get the current sample rate (see <a class="link" href="#opt.lg_prof_sample">
|
||
"<code class="mallctl">opt.lg_prof_sample</code>"
|
||
</a>).
|
||
</p></dd><dt><a name="prof.interval"></a><span class="term">
|
||
|
||
"<code class="mallctl">prof.interval</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-prof</code>]
|
||
</span></dt><dd><p>Average number of bytes allocated between
|
||
inverval-based profile dumps. See the
|
||
<a class="link" href="#opt.lg_prof_interval">
|
||
"<code class="mallctl">opt.lg_prof_interval</code>"
|
||
</a>
|
||
option for additional information.</p></dd><dt><a name="stats.cactive"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.cactive</code>"
|
||
|
||
(<span class="type">size_t *</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Pointer to a counter that contains an approximate count
|
||
of the current number of bytes in active pages. The estimate may be
|
||
high, but never low, because each arena rounds up when computing its
|
||
contribution to the counter. Note that the <a class="link" href="#epoch">
|
||
"<code class="mallctl">epoch</code>"
|
||
</a> mallctl has no bearing
|
||
on this counter. Furthermore, counter consistency is maintained via
|
||
atomic operations, so it is necessary to use an atomic operation in
|
||
order to guarantee a consistent read when dereferencing the pointer.
|
||
</p></dd><dt><a name="stats.allocated"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.allocated</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Total number of bytes allocated by the
|
||
application.</p></dd><dt><a name="stats.active"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.active</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Total number of bytes in active pages allocated by the
|
||
application. This is a multiple of the page size, and greater than or
|
||
equal to <a class="link" href="#stats.allocated">
|
||
"<code class="mallctl">stats.allocated</code>"
|
||
</a>.
|
||
This does not include <a class="link" href="#stats.arenas.i.pdirty">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.pdirty</code>"
|
||
</a>, nor pages
|
||
entirely devoted to allocator metadata.</p></dd><dt><a name="stats.metadata"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.metadata</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Total number of bytes dedicated to metadata, which
|
||
comprise base allocations used for bootstrap-sensitive internal
|
||
allocator data structures, arena chunk headers (see <a class="link" href="#stats.arenas.i.metadata.mapped">
|
||
"<code class="mallctl">stats.arenas.<i>.metadata.mapped</code>"
|
||
</a>),
|
||
and internal allocations (see <a class="link" href="#stats.arenas.i.metadata.allocated">
|
||
"<code class="mallctl">stats.arenas.<i>.metadata.allocated</code>"
|
||
</a>).</p></dd><dt><a name="stats.resident"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.resident</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Maximum number of bytes in physically resident data
|
||
pages mapped by the allocator, comprising all pages dedicated to
|
||
allocator metadata, pages backing active allocations, and unused dirty
|
||
pages. This is a maximum rather than precise because pages may not
|
||
actually be physically resident if they correspond to demand-zeroed
|
||
virtual memory that has not yet been touched. This is a multiple of the
|
||
page size, and is larger than <a class="link" href="#stats.active">
|
||
"<code class="mallctl">stats.active</code>"
|
||
</a>.</p></dd><dt><a name="stats.mapped"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.mapped</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Total number of bytes in active chunks mapped by the
|
||
allocator. This is a multiple of the chunk size, and is larger than
|
||
<a class="link" href="#stats.active">
|
||
"<code class="mallctl">stats.active</code>"
|
||
</a>.
|
||
This does not include inactive chunks, even those that contain unused
|
||
dirty pages, which means that there is no strict ordering between this
|
||
and <a class="link" href="#stats.resident">
|
||
"<code class="mallctl">stats.resident</code>"
|
||
</a>.</p></dd><dt><a name="stats.arenas.i.dss"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.dss</code>"
|
||
|
||
(<span class="type">const char *</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>dss (<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>) allocation precedence as
|
||
related to <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> allocation. See <a class="link" href="#opt.dss">
|
||
"<code class="mallctl">opt.dss</code>"
|
||
</a> for details.
|
||
</p></dd><dt><a name="stats.arenas.i.lg_dirty_mult"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.lg_dirty_mult</code>"
|
||
|
||
(<span class="type">ssize_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Minimum ratio (log base 2) of active to dirty pages.
|
||
See <a class="link" href="#opt.lg_dirty_mult">
|
||
"<code class="mallctl">opt.lg_dirty_mult</code>"
|
||
</a>
|
||
for details.</p></dd><dt><a name="stats.arenas.i.nthreads"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.nthreads</code>"
|
||
|
||
(<span class="type">unsigned</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Number of threads currently assigned to
|
||
arena.</p></dd><dt><a name="stats.arenas.i.pactive"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.pactive</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Number of pages in active runs.</p></dd><dt><a name="stats.arenas.i.pdirty"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.pdirty</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
</span></dt><dd><p>Number of pages within unused runs that are potentially
|
||
dirty, and for which <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>,
|
||
<em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or
|
||
similar has not been called.</p></dd><dt><a name="stats.arenas.i.mapped"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.mapped</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Number of mapped bytes.</p></dd><dt><a name="stats.arenas.i.metadata.mapped"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.metadata.mapped</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Number of mapped bytes in arena chunk headers, which
|
||
track the states of the non-metadata pages.</p></dd><dt><a name="stats.arenas.i.metadata.allocated"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.metadata.allocated</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Number of bytes dedicated to internal allocations.
|
||
Internal allocations differ from application-originated allocations in
|
||
that they are for internal use, and that they are omitted from heap
|
||
profiles. This statistic is reported separately from <a class="link" href="#stats.metadata">
|
||
"<code class="mallctl">stats.metadata</code>"
|
||
</a> and
|
||
<a class="link" href="#stats.arenas.i.metadata.mapped">
|
||
"<code class="mallctl">stats.arenas.<i>.metadata.mapped</code>"
|
||
</a>
|
||
because it overlaps with e.g. the <a class="link" href="#stats.allocated">
|
||
"<code class="mallctl">stats.allocated</code>"
|
||
</a> and
|
||
<a class="link" href="#stats.active">
|
||
"<code class="mallctl">stats.active</code>"
|
||
</a>
|
||
statistics, whereas the other metadata statistics do
|
||
not.</p></dd><dt><a name="stats.arenas.i.npurge"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.npurge</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Number of dirty page purge sweeps performed.
|
||
</p></dd><dt><a name="stats.arenas.i.nmadvise"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.nmadvise</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Number of <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>,
|
||
<em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or
|
||
similar calls made to purge dirty pages.</p></dd><dt><a name="stats.arenas.i.purged"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.purged</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Number of pages purged.</p></dd><dt><a name="stats.arenas.i.small.allocated"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.small.allocated</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Number of bytes currently allocated by small objects.
|
||
</p></dd><dt><a name="stats.arenas.i.small.nmalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.small.nmalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of allocation requests served by
|
||
small bins.</p></dd><dt><a name="stats.arenas.i.small.ndalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.small.ndalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of small objects returned to bins.
|
||
</p></dd><dt><a name="stats.arenas.i.small.nrequests"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.small.nrequests</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of small allocation requests.
|
||
</p></dd><dt><a name="stats.arenas.i.large.allocated"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.large.allocated</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Number of bytes currently allocated by large objects.
|
||
</p></dd><dt><a name="stats.arenas.i.large.nmalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.large.nmalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of large allocation requests served
|
||
directly by the arena.</p></dd><dt><a name="stats.arenas.i.large.ndalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.large.ndalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of large deallocation requests served
|
||
directly by the arena.</p></dd><dt><a name="stats.arenas.i.large.nrequests"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.large.nrequests</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of large allocation requests.
|
||
</p></dd><dt><a name="stats.arenas.i.huge.allocated"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.huge.allocated</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Number of bytes currently allocated by huge objects.
|
||
</p></dd><dt><a name="stats.arenas.i.huge.nmalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.huge.nmalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of huge allocation requests served
|
||
directly by the arena.</p></dd><dt><a name="stats.arenas.i.huge.ndalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.huge.ndalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of huge deallocation requests served
|
||
directly by the arena.</p></dd><dt><a name="stats.arenas.i.huge.nrequests"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.huge.nrequests</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of huge allocation requests.
|
||
</p></dd><dt><a name="stats.arenas.i.bins.j.nmalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.bins.<j>.nmalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of allocations served by bin.
|
||
</p></dd><dt><a name="stats.arenas.i.bins.j.ndalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.bins.<j>.ndalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of allocations returned to bin.
|
||
</p></dd><dt><a name="stats.arenas.i.bins.j.nrequests"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.bins.<j>.nrequests</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of allocation
|
||
requests.</p></dd><dt><a name="stats.arenas.i.bins.j.curregs"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.bins.<j>.curregs</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Current number of regions for this size
|
||
class.</p></dd><dt><a name="stats.arenas.i.bins.j.nfills"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.bins.<j>.nfills</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>]
|
||
</span></dt><dd><p>Cumulative number of tcache fills.</p></dd><dt><a name="stats.arenas.i.bins.j.nflushes"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.bins.<j>.nflushes</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>]
|
||
</span></dt><dd><p>Cumulative number of tcache flushes.</p></dd><dt><a name="stats.arenas.i.bins.j.nruns"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.bins.<j>.nruns</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of runs created.</p></dd><dt><a name="stats.arenas.i.bins.j.nreruns"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.bins.<j>.nreruns</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of times the current run from which
|
||
to allocate changed.</p></dd><dt><a name="stats.arenas.i.bins.j.curruns"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.bins.<j>.curruns</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Current number of runs.</p></dd><dt><a name="stats.arenas.i.lruns.j.nmalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.lruns.<j>.nmalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of allocation requests for this size
|
||
class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.lruns.j.ndalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.lruns.<j>.ndalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of deallocation requests for this
|
||
size class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.lruns.j.nrequests"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.lruns.<j>.nrequests</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of allocation requests for this size
|
||
class.</p></dd><dt><a name="stats.arenas.i.lruns.j.curruns"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.lruns.<j>.curruns</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Current number of runs for this size class.
|
||
</p></dd><dt><a name="stats.arenas.i.hchunks.j.nmalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.hchunks.<j>.nmalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of allocation requests for this size
|
||
class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.hchunks.j.ndalloc"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.hchunks.<j>.ndalloc</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of deallocation requests for this
|
||
size class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.hchunks.j.nrequests"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.hchunks.<j>.nrequests</code>"
|
||
|
||
(<span class="type">uint64_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Cumulative number of allocation requests for this size
|
||
class.</p></dd><dt><a name="stats.arenas.i.hchunks.j.curhchunks"></a><span class="term">
|
||
|
||
"<code class="mallctl">stats.arenas.<i>.hchunks.<j>.curhchunks</code>"
|
||
|
||
(<span class="type">size_t</span>)
|
||
<code class="literal">r-</code>
|
||
[<code class="option">--enable-stats</code>]
|
||
</span></dt><dd><p>Current number of huge allocations for this size class.
|
||
</p></dd></dl></div></div><div class="refsect1"><a name="debugging_malloc_problems"></a><h2>DEBUGGING MALLOC PROBLEMS</h2><p>When debugging, it is a good idea to configure/build jemalloc with
|
||
the <code class="option">--enable-debug</code> and <code class="option">--enable-fill</code>
|
||
options, and recompile the program with suitable options and symbols for
|
||
debugger support. When so configured, jemalloc incorporates a wide variety
|
||
of run-time assertions that catch application errors such as double-free,
|
||
write-after-free, etc.</p><p>Programs often accidentally depend on “uninitialized”
|
||
memory actually being filled with zero bytes. Junk filling
|
||
(see the <a class="link" href="#opt.junk">
|
||
"<code class="mallctl">opt.junk</code>"
|
||
</a>
|
||
option) tends to expose such bugs in the form of obviously incorrect
|
||
results and/or coredumps. Conversely, zero
|
||
filling (see the <a class="link" href="#opt.zero">
|
||
"<code class="mallctl">opt.zero</code>"
|
||
</a> option) eliminates
|
||
the symptoms of such bugs. Between these two options, it is usually
|
||
possible to quickly detect, diagnose, and eliminate such bugs.</p><p>This implementation does not provide much detail about the problems
|
||
it detects, because the performance impact for storing such information
|
||
would be prohibitive. However, jemalloc does integrate with the most
|
||
excellent <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a> tool if the
|
||
<code class="option">--enable-valgrind</code> configuration option is enabled.</p></div><div class="refsect1"><a name="diagnostic_messages"></a><h2>DIAGNOSTIC MESSAGES</h2><p>If any of the memory allocation/deallocation functions detect an
|
||
error or warning condition, a message will be printed to file descriptor
|
||
<code class="constant">STDERR_FILENO</code>. Errors will result in the process
|
||
dumping core. If the <a class="link" href="#opt.abort">
|
||
"<code class="mallctl">opt.abort</code>"
|
||
</a> option is set, most
|
||
warnings are treated as errors.</p><p>The <code class="varname">malloc_message</code> variable allows the programmer
|
||
to override the function which emits the text strings forming the errors
|
||
and warnings if for some reason the <code class="constant">STDERR_FILENO</code> file
|
||
descriptor is not suitable for this.
|
||
<code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) takes the
|
||
<em class="parameter"><code>cbopaque</code></em> pointer argument that is
|
||
<code class="constant">NULL</code> unless overridden by the arguments in a call to
|
||
<code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>), followed by a string
|
||
pointer. Please note that doing anything which tries to allocate memory in
|
||
this function is likely to result in a crash or deadlock.</p><p>All messages are prefixed by
|
||
“<code class="computeroutput"><jemalloc>: </code>”.</p></div><div class="refsect1"><a name="return_values"></a><h2>RETURN VALUES</h2><div class="refsect2"><a name="idp46949776"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) and
|
||
<code class="function">calloc</code>(<em class="parameter"><code></code></em>) functions return a pointer to the
|
||
allocated memory if successful; otherwise a <code class="constant">NULL</code>
|
||
pointer is returned and <code class="varname">errno</code> is set to
|
||
<span class="errorname">ENOMEM</span>.</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function
|
||
returns the value 0 if successful; otherwise it returns an error value.
|
||
The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function will fail
|
||
if:
|
||
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p>The <em class="parameter"><code>alignment</code></em> parameter is
|
||
not a power of 2 at least as large as
|
||
<code class="code">sizeof(<span class="type">void *</span>)</code>.
|
||
</p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
|
||
</p><p>The <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function returns
|
||
a pointer to the allocated memory if successful; otherwise a
|
||
<code class="constant">NULL</code> pointer is returned and
|
||
<code class="varname">errno</code> is set. The
|
||
<code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function will fail if:
|
||
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p>The <em class="parameter"><code>alignment</code></em> parameter is
|
||
not a power of 2.
|
||
</p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
|
||
</p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function returns a
|
||
pointer, possibly identical to <em class="parameter"><code>ptr</code></em>, to the
|
||
allocated memory if successful; otherwise a <code class="constant">NULL</code>
|
||
pointer is returned, and <code class="varname">errno</code> is set to
|
||
<span class="errorname">ENOMEM</span> if the error was the result of an
|
||
allocation failure. The <code class="function">realloc</code>(<em class="parameter"><code></code></em>)
|
||
function always leaves the original buffer intact when an error occurs.
|
||
</p><p>The <code class="function">free</code>(<em class="parameter"><code></code></em>) function returns no
|
||
value.</p></div><div class="refsect2"><a name="idp46974576"></a><h3>Non-standard API</h3><p>The <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) and
|
||
<code class="function">rallocx</code>(<em class="parameter"><code></code></em>) functions return a pointer to
|
||
the allocated memory if successful; otherwise a <code class="constant">NULL</code>
|
||
pointer is returned to indicate insufficient contiguous memory was
|
||
available to service the allocation request. </p><p>The <code class="function">xallocx</code>(<em class="parameter"><code></code></em>) function returns the
|
||
real size of the resulting resized allocation pointed to by
|
||
<em class="parameter"><code>ptr</code></em>, which is a value less than
|
||
<em class="parameter"><code>size</code></em> if the allocation could not be adequately
|
||
grown in place. </p><p>The <code class="function">sallocx</code>(<em class="parameter"><code></code></em>) function returns the
|
||
real size of the allocation pointed to by <em class="parameter"><code>ptr</code></em>.
|
||
</p><p>The <code class="function">nallocx</code>(<em class="parameter"><code></code></em>) returns the real size
|
||
that would result from a successful equivalent
|
||
<code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function call, or zero if
|
||
insufficient memory is available to perform the size computation. </p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>),
|
||
<code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>), and
|
||
<code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>) functions return 0 on
|
||
success; otherwise they return an error value. The functions will fail
|
||
if:
|
||
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p><em class="parameter"><code>newp</code></em> is not
|
||
<code class="constant">NULL</code>, and <em class="parameter"><code>newlen</code></em> is too
|
||
large or too small. Alternatively, <em class="parameter"><code>*oldlenp</code></em>
|
||
is too large or too small; in this case as much data as possible
|
||
are read despite the error.</p></dd><dt><span class="term"><span class="errorname">ENOENT</span></span></dt><dd><p><em class="parameter"><code>name</code></em> or
|
||
<em class="parameter"><code>mib</code></em> specifies an unknown/invalid
|
||
value.</p></dd><dt><span class="term"><span class="errorname">EPERM</span></span></dt><dd><p>Attempt to read or write void value, or attempt to
|
||
write read-only value.</p></dd><dt><span class="term"><span class="errorname">EAGAIN</span></span></dt><dd><p>A memory allocation failure
|
||
occurred.</p></dd><dt><span class="term"><span class="errorname">EFAULT</span></span></dt><dd><p>An interface with side effects failed in some way
|
||
not directly related to <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>)
|
||
read/write processing.</p></dd></dl></div><p>
|
||
</p><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function
|
||
returns the usable size of the allocation pointed to by
|
||
<em class="parameter"><code>ptr</code></em>. </p></div></div><div class="refsect1"><a name="environment"></a><h2>ENVIRONMENT</h2><p>The following environment variable affects the execution of the
|
||
allocation functions:
|
||
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">MALLOC_CONF</code></span></dt><dd><p>If the environment variable
|
||
<code class="envar">MALLOC_CONF</code> is set, the characters it contains
|
||
will be interpreted as options.</p></dd></dl></div><p>
|
||
</p></div><div class="refsect1"><a name="examples"></a><h2>EXAMPLES</h2><p>To dump core whenever a problem occurs:
|
||
</p><pre class="screen">ln -s 'abort:true' /etc/malloc.conf</pre><p>
|
||
</p><p>To specify in the source a chunk size that is 16 MiB:
|
||
</p><pre class="programlisting">
|
||
malloc_conf = "lg_chunk:24";</pre></div><div class="refsect1"><a name="see_also"></a><h2>SEE ALSO</h2><p><span class="citerefentry"><span class="refentrytitle">madvise</span>(2)</span>,
|
||
<span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span>,
|
||
<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>,
|
||
<span class="citerefentry"><span class="refentrytitle">utrace</span>(2)</span>,
|
||
<span class="citerefentry"><span class="refentrytitle">alloca</span>(3)</span>,
|
||
<span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span>,
|
||
<span class="citerefentry"><span class="refentrytitle">getpagesize</span>(3)</span></p></div><div class="refsect1"><a name="standards"></a><h2>STANDARDS</h2><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>),
|
||
<code class="function">calloc</code>(<em class="parameter"><code></code></em>),
|
||
<code class="function">realloc</code>(<em class="parameter"><code></code></em>), and
|
||
<code class="function">free</code>(<em class="parameter"><code></code></em>) functions conform to ISO/IEC
|
||
9899:1990 (“ISO C90”).</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function conforms
|
||
to IEEE Std 1003.1-2001 (“POSIX.1”).</p></div></div></body></html>
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