On Tue, Oct 15, 2024 at 6:33 AM Rong Xu <xur@xxxxxxxxxx> wrote: > +Customization > +============= > + > +You can enable or disable AutoFDO build for individual file and directories by > +adding a line similar to the following to the respective kernel Makefile: Perhaps, it might be worth mentioning that kernel space objects are covered by default. Then, people would understand ':= y' will be less common than ':= n'. > + > +- For enabling a single file (e.g. foo.o) :: > + > + AUTOFDO_PROFILE_foo.o := y > + > +- For enabling all files in one directory :: > + > + AUTOFDO_PROFILE := y > + > +- For disabling one file :: > + > + AUTOFDO_PROFILE_foo.o := n > + > +- For disabling all files in one directory :: > + > + AUTOFDO_PROFILE := n > + > +3) 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: For Intel platforms: I guess this is a copy-paste mistake. For AMD platforms: For Intel platforms: -> For AMD platforms: > + (https://github.com/google/autofdo), version v0.30.1 or later. Please one space instead of two after the comma. > diff --git a/scripts/Makefile.autofdo b/scripts/Makefile.autofdo > new file mode 100644 > index 000000000000..1c9f224bc221 > --- /dev/null > +++ b/scripts/Makefile.autofdo > @@ -0,0 +1,23 @@ > +# SPDX-License-Identifier: GPL-2.0 > + > +# Enable available and selected Clang AutoFDO features. > + > +CFLAGS_AUTOFDO_CLANG := -fdebug-info-for-profiling -mllvm -enable-fs-discriminator=true -mllvm -improved-fs-discriminator=true > + > +# If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. Meaningless comment. It explains too obvious code. > +ifndef CONFIG_DEBUG_INFO > + CFLAGS_AUTOFDO_CLANG += -gmlt > +endif > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib > index 01a9f567d5af..e85d6ac31bd9 100644 > --- a/scripts/Makefile.lib > +++ b/scripts/Makefile.lib > @@ -191,6 +191,16 @@ _c_flags += $(if $(patsubst n%,, \ > -D__KCSAN_INSTRUMENT_BARRIERS__) > endif > > +# > +# Enable Clang's AutoFDO build flags for a file or directory depending on > +# variables AUTOFDO_PROFILE_obj.o and AUTOFDO_PROFILE. > +# This comment would give the wrong understanding that this flag is opt-in. The comment for KASAN correctly describes that it is enabled by default, and can be opted out using KASAN_SANITIZE_*. -- Best Regards Masahiro Yamada
