€•¡e      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ%/translations/zh_CN/dev-tools/autofdo”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/zh_TW/dev-tools/autofdo”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/it_IT/dev-tools/autofdo”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/ja_JP/dev-tools/autofdo”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/ko_KR/dev-tools/autofdo”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒPortuguese (Brazilian)”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/pt_BR/dev-tools/autofdo”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh–sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/sp_SP/dev-tools/autofdo”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ SPDX-License-Identifier: GPL-2.0”h]”hŒ SPDX-License-Identifier: GPL-2.0”…””}”hh·sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1hµhhh²hh³Œ?/var/lib/git/docbuild/linux/Documentation/dev-tools/autofdo.rst”h´KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒ#Using AutoFDO with the Linux kernel”h]”hŒ#Using AutoFDO with the Linux kernel”…””}”(hhÏh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhhÊh²hh³hÇh´KubhŒ	paragraph”“”)”}”(hX†  This enables AutoFDO build support for the kernel when using
the Clang compiler. AutoFDO (Auto-Feedback-Directed Optimization)
is a type of profile-guided optimization (PGO) used to enhance the
performance of binary executables. It gathers information about the
frequency of execution of various code paths within a binary using
hardware sampling. This data is then used to guide the compiler's
optimization decisions, resulting in a more efficient binary. AutoFDO
is a powerful optimization technique, and data indicates that it can
significantly improve kernel performance. It's especially beneficial
for workloads affected by front-end stalls.”h]”hXŠ  This enables AutoFDO build support for the kernel when using
the Clang compiler. AutoFDO (Auto-Feedback-Directed Optimization)
is a type of profile-guided optimization (PGO) used to enhance the
performance of binary executables. It gathers information about the
frequency of execution of various code paths within a binary using
hardware sampling. This data is then used to guide the compilerâ€™s
optimization decisions, resulting in a more efficient binary. AutoFDO
is a powerful optimization technique, and data indicates that it can
significantly improve kernel performance. Itâ€™s especially beneficial
for workloads affected by front-end stalls.”…””}”(hhßh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KhhÊh²hubhÞ)”}”(hXâ  For AutoFDO builds, unlike non-FDO builds, the user must supply a
profile. Acquiring an AutoFDO profile can be done in several ways.
AutoFDO profiles are created by converting hardware sampling using
the "perf" tool. It is crucial that the workload used to create these
perf files is representative; they must exhibit runtime
characteristics similar to the workloads that are intended to be
optimized. Failure to do so will result in the compiler optimizing
for the wrong objective.”h]”hXæ  For AutoFDO builds, unlike non-FDO builds, the user must supply a
profile. Acquiring an AutoFDO profile can be done in several ways.
AutoFDO profiles are created by converting hardware sampling using
the â€œperfâ€ tool. It is crucial that the workload used to create these
perf files is representative; they must exhibit runtime
characteristics similar to the workloads that are intended to be
optimized. Failure to do so will result in the compiler optimizing
for the wrong objective.”…””}”(hhíh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KhhÊh²hubhÞ)”}”(hXX  The AutoFDO profile often encapsulates the program's behavior. If the
performance-critical codes are architecture-independent, the profile
can be applied across platforms to achieve performance gains. For
instance, using the profile generated on Intel architecture to build
a kernel for AMD architecture can also yield performance improvements.”h]”hXZ  The AutoFDO profile often encapsulates the programâ€™s behavior. If the
performance-critical codes are architecture-independent, the profile
can be applied across platforms to achieve performance gains. For
instance, using the profile generated on Intel architecture to build
a kernel for AMD architecture can also yield performance improvements.”…””}”(hhûh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KhhÊh²hubhÞ)”}”(hXB  There are two methods for acquiring a representative profile:
(1) Sample real workloads using a production environment.
(2) Generate the profile using a representative load test.
When enabling the AutoFDO build configuration without providing an
AutoFDO profile, the compiler only modifies the dwarf information in
the kernel without impacting runtime performance. It's advisable to
use a kernel binary built with the same AutoFDO configuration to
collect the perf profile. While it's possible to use a kernel built
with different options, it may result in inferior performance.”h]”hXF  There are two methods for acquiring a representative profile:
(1) Sample real workloads using a production environment.
(2) Generate the profile using a representative load test.
When enabling the AutoFDO build configuration without providing an
AutoFDO profile, the compiler only modifies the dwarf information in
the kernel without impacting runtime performance. Itâ€™s advisable to
use a kernel binary built with the same AutoFDO configuration to
collect the perf profile. While itâ€™s possible to use a kernel built
with different options, it may result in inferior performance.”…””}”(hj	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K!hhÊh²hubhÞ)”}”(hŒýOne can collect profiles using AutoFDO build for the previous kernel.
AutoFDO employs relative line numbers to match the profiles, offering
some tolerance for source changes. This mode is commonly used in a
production environment for profile collection.”h]”hŒýOne can collect profiles using AutoFDO build for the previous kernel.
AutoFDO employs relative line numbers to match the profiles, offering
some tolerance for source changes. This mode is commonly used in a
production environment for profile collection.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K+hhÊh²hubhÞ)”}”(hŒmIn a profile collection based on a load test, the AutoFDO collection
process consists of the following steps:”h]”hŒmIn a profile collection based on a load test, the AutoFDO collection
process consists of the following steps:”…””}”(hj%  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K0hhÊh²hubhŒenumerated_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒKInitial build: The kernel is built with AutoFDO options
without a profile.
”h]”hÞ)”}”(hŒJInitial build: The kernel is built with AutoFDO options
without a profile.”h]”hŒJInitial build: The kernel is built with AutoFDO options
without a profile.”…””}”(hj>  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K3hj:  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j8  hj5  h²hh³hÇh´Nubj9  )”}”(hX	  Profiling: The above kernel is then run with a representative
workload to gather execution frequency data. This data is
collected using hardware sampling, via perf. AutoFDO is most
effective on platforms supporting advanced PMU features like
LBR on Intel machines.
”h]”hÞ)”}”(hX  Profiling: The above kernel is then run with a representative
workload to gather execution frequency data. This data is
collected using hardware sampling, via perf. AutoFDO is most
effective on platforms supporting advanced PMU features like
LBR on Intel machines.”h]”hX  Profiling: The above kernel is then run with a representative
workload to gather execution frequency data. This data is
collected using hardware sampling, via perf. AutoFDO is most
effective on platforms supporting advanced PMU features like
LBR on Intel machines.”…””}”(hjV  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K6hjR  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j8  hj5  h²hh³hÇh´Nubj9  )”}”(hŒdAutoFDO profile generation: Perf output file is converted to
the AutoFDO profile via offline tools.
”h]”hÞ)”}”(hŒcAutoFDO profile generation: Perf output file is converted to
the AutoFDO profile via offline tools.”h]”hŒcAutoFDO profile generation: Perf output file is converted to
the AutoFDO profile via offline tools.”…””}”(hjn  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K<hjj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j8  hj5  h²hh³hÇh´Nubeh}”(h]”h ]”h"]”h$]”h&]”Œenumtype”Œarabic”Œprefix”hŒsuffix”Œ.”uh1j3  hhÊh²hh³hÇh´K3ubhÞ)”}”(hŒ7The support requires a Clang compiler LLVM 17 or later.”h]”hŒ7The support requires a Clang compiler LLVM 17 or later.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K?hhÊh²hubhÉ)”}”(hhh]”(hÎ)”}”(hŒPreparation”h]”hŒPreparation”…””}”(hjž  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhj›  h²hh³hÇh´KBubhÞ)”}”(hŒConfigure the kernel with::”h]”hŒConfigure the kernel with:”…””}”(hj¬  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KDhj›  h²hubhŒliteral_block”“”)”}”(hŒCONFIG_AUTOFDO_CLANG=y”h]”hŒCONFIG_AUTOFDO_CLANG=y”…””}”hj¼  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´KFhj›  h²hubeh}”(h]”Œpreparation”ah ]”h"]”Œpreparation”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´KBubhÉ)”}”(hhh]”(hÎ)”}”(hŒCustomization”h]”hŒCustomization”…””}”(hjÕ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhjÒ  h²hh³hÇh´KIubhÞ)”}”(hŒüThe default CONFIG_AUTOFDO_CLANG setting covers kernel space objects for
AutoFDO builds. One can, however, enable or disable AutoFDO build for
individual files and directories by adding a line similar to the following
to the respective kernel Makefile:”h]”hŒüThe default CONFIG_AUTOFDO_CLANG setting covers kernel space objects for
AutoFDO builds. One can, however, enable or disable AutoFDO build for
individual files and directories by adding a line similar to the following
to the respective kernel Makefile:”…””}”(hjã  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KKhjÒ  h²hubhŒbullet_list”“”)”}”(hhh]”(j9  )”}”(hŒHFor enabling a single file (e.g. foo.o) ::

 AUTOFDO_PROFILE_foo.o := y
”h]”(hÞ)”}”(hŒ*For enabling a single file (e.g. foo.o) ::”h]”hŒ'For enabling a single file (e.g. foo.o)”…””}”(hjú  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KPhjö  ubj»  )”}”(hŒAUTOFDO_PROFILE_foo.o := y”h]”hŒAUTOFDO_PROFILE_foo.o := y”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´KRhjö  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j8  hjó  h²hh³hÇh´Nubj9  )”}”(hŒBFor enabling all files in one directory ::

 AUTOFDO_PROFILE := y
”h]”(hÞ)”}”(hŒ*For enabling all files in one directory ::”h]”hŒ'For enabling all files in one directory”…””}”(hj   h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KThj  ubj»  )”}”(hŒAUTOFDO_PROFILE := y”h]”hŒAUTOFDO_PROFILE := y”…””}”hj.  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´KVhj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j8  hjó  h²hh³hÇh´Nubj9  )”}”(hŒ7For disabling one file ::

 AUTOFDO_PROFILE_foo.o := n
”h]”(hÞ)”}”(hŒFor disabling one file ::”h]”hŒFor disabling one file”…””}”(hjF  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KXhjB  ubj»  )”}”(hŒAUTOFDO_PROFILE_foo.o := n”h]”hŒAUTOFDO_PROFILE_foo.o := n”…””}”hjT  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´KZhjB  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j8  hjó  h²hh³hÇh´Nubj9  )”}”(hŒCFor disabling all files in one directory ::

 AUTOFDO_PROFILE := n
”h]”(hÞ)”}”(hŒ+For disabling all files in one directory ::”h]”hŒ(For disabling all files in one directory”…””}”(hjl  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K\hjh  ubj»  )”}”(hŒAUTOFDO_PROFILE := n”h]”hŒAUTOFDO_PROFILE := n”…””}”hjz  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´K^hjh  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j8  hjó  h²hh³hÇh´Nubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1jñ  h³hÇh´KPhjÒ  h²hubeh}”(h]”Œcustomization”ah ]”h"]”Œcustomization”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´KIubhÉ)”}”(hhh]”(hÎ)”}”(hŒWorkflow”h]”hŒWorkflow”…””}”(hj¡  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhjž  h²hh³hÇh´KaubhÞ)”}”(hŒ/Here is an example workflow for AutoFDO kernel:”h]”hŒ/Here is an example workflow for AutoFDO kernel:”…””}”(hj¯  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´Kchjž  h²hubj4  )”}”(hhh]”(j9  )”}”(hXG  Build the kernel on the host machine with LLVM enabled,
for example, ::

  $ make menuconfig LLVM=1

Turn on AutoFDO build config::

  CONFIG_AUTOFDO_CLANG=y

With a configuration that with LLVM enabled, use the following command::

  $ scripts/config -e AUTOFDO_CLANG

After getting the config, build with ::

  $ make LLVM=1
”h]”(hÞ)”}”(hŒGBuild the kernel on the host machine with LLVM enabled,
for example, ::”h]”hŒDBuild the kernel on the host machine with LLVM enabled,
for example,”…””}”(hjÄ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KehjÀ  ubj»  )”}”(hŒ$ make menuconfig LLVM=1”h]”hŒ$ make menuconfig LLVM=1”…””}”hjÒ  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´KhhjÀ  ubhÞ)”}”(hŒTurn on AutoFDO build config::”h]”hŒTurn on AutoFDO build config:”…””}”(hjà  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KjhjÀ  ubj»  )”}”(hŒCONFIG_AUTOFDO_CLANG=y”h]”hŒCONFIG_AUTOFDO_CLANG=y”…””}”hjî  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´KlhjÀ  ubhÞ)”}”(hŒHWith a configuration that with LLVM enabled, use the following command::”h]”hŒGWith a configuration that with LLVM enabled, use the following command:”…””}”(hjü  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KnhjÀ  ubj»  )”}”(hŒ!$ scripts/config -e AUTOFDO_CLANG”h]”hŒ!$ scripts/config -e AUTOFDO_CLANG”…””}”hj
  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´KphjÀ  ubhÞ)”}”(hŒ'After getting the config, build with ::”h]”hŒ$After getting the config, build with”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KrhjÀ  ubj»  )”}”(hŒ$ make LLVM=1”h]”hŒ$ make LLVM=1”…””}”hj&  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´KthjÀ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j8  hj½  h²hh³hÇh´Nubj9  )”}”(hŒ(Install the kernel on the test machine.
”h]”hÞ)”}”(hŒ'Install the kernel on the test machine.”h]”hŒ'Install the kernel on the test machine.”…””}”(hj>  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´Kvhj:  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j8  hj½  h²hh³hÇh´Nubj9  )”}”(hX’  Run the load tests. The '-c' option in perf specifies the sample
event period. We suggest using a suitable prime number, like 500009,
for this purpose.

- For Intel platforms::

   $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c <count> -o <perf_file> -- <loadtest>

- For AMD platforms:

  The supported systems are: Zen3 with BRS, or Zen4 with amd_lbr_v2. To check,

  For Zen3::

   $ cat /proc/cpuinfo | grep " brs"

  For Zen4::

   $ cat /proc/cpuinfo | grep amd_lbr_v2

  The following command generated the perf data file::

   $ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c <count> -o <perf_file> -- <loadtest>
”h]”(hÞ)”}”(hŒ—Run the load tests. The '-c' option in perf specifies the sample
event period. We suggest using a suitable prime number, like 500009,
for this purpose.”h]”hŒ›Run the load tests. The â€˜-câ€™ option in perf specifies the sample
event period. We suggest using a suitable prime number, like 500009,
for this purpose.”…””}”(hjV  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KxhjR  ubjò  )”}”(hhh]”(j9  )”}”(hŒwFor Intel platforms::

 $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c <count> -o <perf_file> -- <loadtest>
”h]”(hÞ)”}”(hŒFor Intel platforms::”h]”hŒFor Intel platforms:”…””}”(hjk  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K|hjg  ubj»  )”}”(hŒ^$ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c <count> -o <perf_file> -- <loadtest>”h]”hŒ^$ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c <count> -o <perf_file> -- <loadtest>”…””}”hjy  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´K~hjg  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j8  hjd  ubj9  )”}”(hXm  For AMD platforms:

The supported systems are: Zen3 with BRS, or Zen4 with amd_lbr_v2. To check,

For Zen3::

 $ cat /proc/cpuinfo | grep " brs"

For Zen4::

 $ cat /proc/cpuinfo | grep amd_lbr_v2

The following command generated the perf data file::

 $ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c <count> -o <perf_file> -- <loadtest>
”h]”(hÞ)”}”(hŒFor AMD platforms:”h]”hŒFor AMD platforms:”…””}”(hj‘  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K€hj  ubhÞ)”}”(hŒLThe supported systems are: Zen3 with BRS, or Zen4 with amd_lbr_v2. To check,”h]”hŒLThe supported systems are: Zen3 with BRS, or Zen4 with amd_lbr_v2. To check,”…””}”(hjŸ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K‚hj  ubhÞ)”}”(hŒ
For Zen3::”h]”hŒ	For Zen3:”…””}”(hj­  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K„hj  ubj»  )”}”(hŒ!$ cat /proc/cpuinfo | grep " brs"”h]”hŒ!$ cat /proc/cpuinfo | grep " brs"”…””}”hj»  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´K†hj  ubhÞ)”}”(hŒ
For Zen4::”h]”hŒ	For Zen4:”…””}”(hjÉ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´Kˆhj  ubj»  )”}”(hŒ%$ cat /proc/cpuinfo | grep amd_lbr_v2”h]”hŒ%$ cat /proc/cpuinfo | grep amd_lbr_v2”…””}”hj×  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´KŠhj  ubhÞ)”}”(hŒ4The following command generated the perf data file::”h]”hŒ3The following command generated the perf data file:”…””}”(hjå  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´KŒhj  ubj»  )”}”(hŒo$ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c <count> -o <perf_file> -- <loadtest>”h]”hŒo$ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c <count> -o <perf_file> -- <loadtest>”…””}”hjó  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´KŽhj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j8  hjd  ubeh}”(h]”h ]”h"]”h$]”h&]”j”  j•  uh1jñ  h³hÇh´K|hjR  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j8  hj½  h²hh³Nh´Nubj9  )”}”(hŒ;(Optional) Download the raw perf file to the host machine.
”h]”hÞ)”}”(hŒ:(Optional) Download the raw perf file to the host machine.”h]”hŒ:(Optional) Download the raw perf file to the host machine.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´Khj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j8  hj½  h²hh³hÇh´Nubj9  )”}”(hXR  To generate an AutoFDO profile, two offline tools are available:
create_llvm_prof and llvm_profgen. The create_llvm_prof tool is part
of the AutoFDO project and can be found on GitHub
(https://github.com/google/autofdo), version v0.30.1 or later.
The llvm_profgen tool is included in the LLVM compiler itself. It's
important to note that the version of llvm_profgen doesn't need to match
the version of Clang. It needs to be the LLVM 19 release of Clang
or later, or just from the LLVM trunk. ::

   $ llvm-profgen --kernel --binary=<vmlinux> --perfdata=<perf_file> -o <profile_file>

or ::

   $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> --format=extbinary --out=<profile_file>

Note that multiple AutoFDO profile files can be merged into one via::

   $ llvm-profdata merge -o <profile_file> <profile_1> <profile_2> ... <profile_n>
”h]”(hÞ)”}”(hXï  To generate an AutoFDO profile, two offline tools are available:
create_llvm_prof and llvm_profgen. The create_llvm_prof tool is part
of the AutoFDO project and can be found on GitHub
(https://github.com/google/autofdo), version v0.30.1 or later.
The llvm_profgen tool is included in the LLVM compiler itself. It's
important to note that the version of llvm_profgen doesn't need to match
the version of Clang. It needs to be the LLVM 19 release of Clang
or later, or just from the LLVM trunk. ::”h]”(hŒ¹To generate an AutoFDO profile, two offline tools are available:
create_llvm_prof and llvm_profgen. The create_llvm_prof tool is part
of the AutoFDO project and can be found on GitHub
(”…””}”(hj/  h²hh³Nh´NubhŒ	reference”“”)”}”(hŒ!https://github.com/google/autofdo”h]”hŒ!https://github.com/google/autofdo”…””}”(hj9  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”j;  uh1j7  hj/  ubhX  ), version v0.30.1 or later.
The llvm_profgen tool is included in the LLVM compiler itself. Itâ€™s
important to note that the version of llvm_profgen doesnâ€™t need to match
the version of Clang. It needs to be the LLVM 19 release of Clang
or later, or just from the LLVM trunk.”…””}”(hj/  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K’hj+  ubj»  )”}”(hŒS$ llvm-profgen --kernel --binary=<vmlinux> --perfdata=<perf_file> -o <profile_file>”h]”hŒS$ llvm-profgen --kernel --binary=<vmlinux> --perfdata=<perf_file> -o <profile_file>”…””}”hjR  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´K›hj+  ubhÞ)”}”(hŒor ::”h]”hŒor”…””}”(hj`  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´Khj+  ubj»  )”}”(hŒc$ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> --format=extbinary --out=<profile_file>”h]”hŒc$ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> --format=extbinary --out=<profile_file>”…””}”hjn  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´KŸhj+  ubhÞ)”}”(hŒENote that multiple AutoFDO profile files can be merged into one via::”h]”hŒDNote that multiple AutoFDO profile files can be merged into one via:”…””}”(hj|  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K¡hj+  ubj»  )”}”(hŒO$ llvm-profdata merge -o <profile_file> <profile_1> <profile_2> ... <profile_n>”h]”hŒO$ llvm-profdata merge -o <profile_file> <profile_1> <profile_2> ... <profile_n>”…””}”hjŠ  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´K£hj+  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j8  hj½  h²hh³hÇh´Nubj9  )”}”(hŒºRebuild the kernel using the AutoFDO profile file with the same config as step 1,
(Note CONFIG_AUTOFDO_CLANG needs to be enabled)::

   $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<profile_file>”h]”(hÞ)”}”(hŒƒRebuild the kernel using the AutoFDO profile file with the same config as step 1,
(Note CONFIG_AUTOFDO_CLANG needs to be enabled)::”h]”hŒ‚Rebuild the kernel using the AutoFDO profile file with the same config as step 1,
(Note CONFIG_AUTOFDO_CLANG needs to be enabled):”…””}”(hj¢  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝh³hÇh´K¥hjž  ubj»  )”}”(hŒ2$ make LLVM=1 CLANG_AUTOFDO_PROFILE=<profile_file>”h]”hŒ2$ make LLVM=1 CLANG_AUTOFDO_PROFILE=<profile_file>”…””}”hj°  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1jº  h³hÇh´K¨hjž  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j8  hj½  h²hh³hÇh´Nubeh}”(h]”h ]”h"]”h$]”h&]”jˆ  j‰  jŠ  hj‹  Œ)”uh1j3  hjž  h²hh³hÇh´Keubeh}”(h]”Œworkflow”ah ]”h"]”Œworkflow”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´Kaubeh}”(h]”Œ#using-autofdo-with-the-linux-kernel”ah ]”h"]”Œ#using autofdo with the linux kernel”ah$]”h&]”uh1hÈhhh²hh³hÇh´Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”hÇuh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(hÍNŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”jþ  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”hÇŒ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(jØ  jÕ  jÏ  jÌ  j›  j˜  jÐ  jÍ  uŒ	nametypes”}”(jØ  ‰jÏ  ‰j›  ‰jÐ  ‰uh}”(jÕ  hÊjÌ  j›  j˜  jÒ  jÍ  jž  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nh²hub.