1.. SPDX-License-Identifier: BSD-3-Clause 2 Copyright(c) 2019 Marvell International Ltd. 3 4Link Time Optimization 5====================== 6 7The DPDK supports compilation with link time optimization turned on. 8This depends obviously on the ability of the compiler to do "whole 9program" optimization at link time and is available only for compilers 10that support that feature. 11To be more specific, compiler (in addition to performing LTO) have to 12support creation of ELF objects containing both normal code and internal 13representation (called fat-lto-objects in gcc and icc). 14This is required since during build some code is generated by parsing 15produced ELF objects (pmdinfogen). 16 17The amount of performance gain that one can get from LTO depends on the 18compiler and the code that is being compiled. 19However LTO is also useful for additional code analysis done by the 20compiler. 21In particular due to interprocedural analysis compiler can produce 22additional warnings about variables that might be used uninitialized. 23Some of these warnings might be "false positives" though and you might 24need to explicitly initialize variable in order to silence the compiler. 25 26Please note that turning LTO on causes considerable extension of 27build time. 28 29When using make based build, link time optimization can be enabled for 30the whole DPDK by setting: 31 32.. code-block:: console 33 34 CONFIG_RTE_ENABLE_LTO=y 35 36in config file. 37 38For the meson based build it can be enabled by setting meson built-in 39'b_lto' option: 40 41.. code-block:: console 42 43 meson build -Db_lto=true 44