mirror of https://github.com/F-Stack/f-stack.git
44 lines
1.5 KiB
ReStructuredText
44 lines
1.5 KiB
ReStructuredText
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.. SPDX-License-Identifier: BSD-3-Clause
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Copyright(c) 2019 Marvell International Ltd.
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Link Time Optimization
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======================
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The DPDK supports compilation with link time optimization turned on.
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This depends obviously on the ability of the compiler to do "whole
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program" optimization at link time and is available only for compilers
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that support that feature.
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To be more specific, compiler (in addition to performing LTO) have to
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support creation of ELF objects containing both normal code and internal
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representation (called fat-lto-objects in gcc and icc).
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This is required since during build some code is generated by parsing
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produced ELF objects (pmdinfogen).
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The amount of performance gain that one can get from LTO depends on the
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compiler and the code that is being compiled.
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However LTO is also useful for additional code analysis done by the
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compiler.
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In particular due to interprocedural analysis compiler can produce
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additional warnings about variables that might be used uninitialized.
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Some of these warnings might be "false positives" though and you might
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need to explicitly initialize variable in order to silence the compiler.
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Please note that turning LTO on causes considerable extension of
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build time.
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When using make based build, link time optimization can be enabled for
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the whole DPDK by setting:
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.. code-block:: console
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CONFIG_ENABLE_LTO=y
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in config file.
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For the meson based build it can be enabled by setting meson built-in
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'b_lto' option:
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.. code-block:: console
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meson build -Db_lto=true
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