| Message ID | 20241014213342.1480681-7-xur@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add AutoFDO and Propeller support for Clang build | expand |
Please remove the period at the end of the commit subject. On Tue, Oct 15, 2024 at 6:34 AM Rong Xu <xur@google.com> wrote: > > Add the build support for using Clang's Propeller optimizer. Like > AutoFDO, Propeller uses hardware sampling to gather information > about the frequency of execution of different code paths within a > binary. This information is then used to guide the compiler's > optimization decisions, resulting in a more efficient binary. > > The support requires a Clang compiler LLVM 19 or later, and the > create_llvm_prof tool > (https://github.com/google/autofdo/releases/tag/v0.30.1). This > submission is limited to x86 platforms that support PMU features "This submission" -> "This commit" > like LBR on Intel machines and AMD Zen3 BRS. > > For Arm, we plan to send patches for SPE-based Propeller when > AutoFDO for Arm is ready. "we plan to send ..." is not a good description once it is committed. This sentence should be moved to the cover letter, or reworked. > > Here is an example workflow for building an AutoFDO+Propeller > optimized kernel: > > 1) Build the kernel on the HOST machine, with AutoFDO and Propeller Why is the "HOST" capitalized? > build config > CONFIG_AUTOFDO_CLANG=y > CONFIG_PROPELLER_CLANG=y > then > $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile> > > “<autofdo_profile>” is the profile collected when doing a non-Propeller > AutoFDO build. This step builds a kernel that has the same optimization > level as AutoFDO, plus a metadata section that records basic block > information. This kernel image runs as fast as an AutoFDO optimized > kernel. > > 2) Install the kernel on test/production machines. > > 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: > The supported system are: Zen3 with BRS, or Zen4 with amd_lbr_v2 > # To see if Zen3 support LBR: > $ cat proc/cpuinfo | grep " brs" > # To see if Zen4 support LBR: > $ cat proc/cpuinfo | grep amd_lbr_v2 > # If the result is yes, then collect the profile using: > $ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a \ > -N -b -c <count> -o <perf_file> -- <loadtest> > > 4) (Optional) Download the raw perf file to the HOST machine. Same question as above. > > 5) Generate Propeller profile: > $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> \ > --format=propeller --propeller_output_module_name \ > --out=<propeller_profile_prefix>_cc_profile.txt \ > --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt > > “create_llvm_prof” is the profile conversion tool, and a prebuilt > binary for linux can be found on > https://github.com/google/autofdo/releases/tag/v0.30.1 (can also build > from source). > > "<propeller_profile_prefix>" can be something like > "/home/user/dir/any_string". > > This command generates a pair of Propeller profiles: > "<propeller_profile_prefix>_cc_profile.txt" and > "<propeller_profile_prefix>_ld_profile.txt". > > 6) Rebuild the kernel using the AutoFDO and Propeller profile files. > CONFIG_AUTOFDO_CLANG=y > CONFIG_PROPELLER_CLANG=y > and > $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile> \ > CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix> > > Co-developed-by: Han Shen <shenhan@google.com> > Signed-off-by: Han Shen <shenhan@google.com> > Signed-off-by: Rong Xu <xur@google.com> > Suggested-by: Sriraman Tallam <tmsriram@google.com> > Suggested-by: Krzysztof Pszeniczny <kpszeniczny@google.com> > Suggested-by: Nick Desaulniers <ndesaulniers@google.com> > Suggested-by: Stephane Eranian <eranian@google.com> > > .. only:: subproject and html > diff --git a/Documentation/dev-tools/propeller.rst b/Documentation/dev-tools/propeller.rst > new file mode 100644 > index 000000000000..a217354e0f95 > --- /dev/null > +++ b/Documentation/dev-tools/propeller.rst > @@ -0,0 +1,161 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +===================================== > +Using Propeller with the Linux kernel > +===================================== > + > +This enables Propeller build support for the kernel when using Clang > +compiler. Propeller is a profile-guided optimization (PGO) method used > +to optimize binary executables. Like AutoFDO, it utilizes hardware > +sampling to gather information about the frequency of execution of > +different code paths within a binary. Unlike AutoFDO, this information > +is then used right before linking phase to optimize (among others) > +block layout within and across functions. > + > +A few important notes about adopting Propeller optimization: > + > +#. Although it can be used as a standalone optimization step, it is > + strongly recommended to apply Propeller on top of AutoFDO, > + AutoFDO+ThinLTO or Instrument FDO. The rest of this document > + assumes this paradigm. This is a hard requirement instead of a recommendation because PROPERLLER_CLANG has "depends on AUTOFDO_CLANG". > + > +#. Propeller uses another round of profiling on top of > + AutoFDO/AutoFDO+ThinLTO/iFDO. The whole build process involves > + "build-afdo - train-afdo - build-propeller - train-propeller - > + build-optimized". > + > +#. Propeller requires LLVM 19 release or later for Clang/Clang++ > + and the linker(ld.lld). > + > +#. In addition to LLVM toolchain, Propeller requires a profiling > + conversion tool: https://github.com/google/autofdo with a release > + after v0.30.1: https://github.com/google/autofdo/releases/tag/v0.30.1. > + > +The Propeller optimization process involves the following steps: > + > +#. Initial building: Build the AutoFDO or AutoFDO+ThinLTO binary as > + you would normally do, but with a set of compile-time / link-time > + flags, so that a special metadata section is created within the > + kernel binary. The special section is only intend to be used by the > + profiling tool, it is not part of the runtime image, nor does it > + change kernel run time text sections. > + > +#. 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. Propeller is most effective on > + platforms supporting advanced PMU features like LBR on Intel > + machines. This step is the same as profiling the kernel for AutoFDO > + (the exact perf parameters can be different). > + > +#. Propeller profile generation: Perf output file is converted to a > + pair of Propeller profiles via an offline tool. > + > +#. Optimized build: Build the AutoFDO or AutoFDO+ThinLTO optimized > + binary as you would normally do, but with a compile-time / > + link-time flag to pick up the Propeller compile time and link time > + profiles. This build step uses 3 profiles - the AutoFDO profile, > + the Propeller compile-time profile and the Propeller link-time > + profile. > + > +#. Deployment: The optimized kernel binary is deployed and used > + in production environments, providing improved performance > + and reduced latency. > + > +Preparation > +=========== > + > +Configure the kernel with:: > + > + CONFIG_AUTOFDO_CLANG=y This is automatically met due to "depends on AUTOFDO_CLANG". > + CONFIG_PROPELLER_CLANG=y > + > +Customization > +============= > + > +You can enable or disable Propeller build for individual file and > +directories by adding a line similar to the following to the > +respective kernel Makefile: The same comment as in 1/6. > +- For enabling a single file (e.g. foo.o):: > + > + PROPELLER_PROFILE_foo.o := y > + > +- For enabling all files in one directory:: > + > + PROPELLER_PROFILE := y > + > +- For disabling one file:: > + > + PROPELLER_PROFILE_foo.o := n > + > +- For disabling all files in one directory:: > + > + PROPELLER__PROFILE := n > + > + > +Workflow > +======== > + > +Here is an example workflow for building an AutoFDO+Propeller kernel: > + > +1) Assuming an AutoFDO profile is already collected following > + instructions in the AutoFDO document, build the kernel on the HOST > + machine, with AutoFDO and Propeller build configs :: > + > + CONFIG_AUTOFDO_CLANG=y > + CONFIG_PROPELLER_CLANG=y > + > + and :: > + > + $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo-profile-name> > + > +2) Install the kernel on the TEST machine. I am repeatedly encountered with capitalized "HOST" and "TEST". Does this term have a special meaning instead of a test machine in general? > + > +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:: > + > + $ perf record --pfm-event RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c <count> -o <perf_file> -- <loadtest> > + > + Note you can repeat the above steps to collect multiple <perf_file>s. > + > +4) (Optional) Download the raw perf file(s) to the HOST machine. > + > +5) Use the create_llvm_prof tool (https://github.com/google/autofdo) to > + generate Propeller profile. :: > + > + $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> > + --format=propeller --propeller_output_module_name > + --out=<propeller_profile_prefix>_cc_profile.txt > + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt > + > + "<propeller_profile_prefix>" can be something like "/home/user/dir/any_string". > + > + This command generates a pair of Propeller profiles: > + "<propeller_profile_prefix>_cc_profile.txt" and > + "<propeller_profile_prefix>_ld_profile.txt". > + > + If there are more than 1 perf_file collected in the previous step, > + you can create a temp list file "<perf_file_list>" with each line > + containing one perf file name and run:: > + > + $ create_llvm_prof --binary=<vmlinux> --profile=@<perf_file_list> > + --format=propeller --propeller_output_module_name > + --out=<propeller_profile_prefix>_cc_profile.txt > + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt > + > +6) Rebuild the kernel using the AutoFDO and Propeller > + profiles. :: "." and "::" are an odd combination. > + > + CONFIG_AUTOFDO_CLANG=y > + CONFIG_PROPELLER_CLANG=y > + > + and :: > + > + $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<profile_file> CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix> > diff --git a/Makefile b/Makefile > index bbb6ec68f5dc..2d2f688c21c6 100644 > --- a/Makefile > +++ b/Makefile > @@ -1019,6 +1019,7 @@ include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan > include-$(CONFIG_KCOV) += scripts/Makefile.kcov > include-$(CONFIG_RANDSTRUCT) += scripts/Makefile.randstruct > include-$(CONFIG_AUTOFDO_CLANG) += scripts/Makefile.autofdo > +include-$(CONFIG_PROPELLER_CLANG) += scripts/Makefile.propeller > include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins > > include $(addprefix $(srctree)/, $(include-y)) > diff --git a/arch/Kconfig b/arch/Kconfig > index 5e9604960cbb..fdeb5f173a10 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -831,6 +831,28 @@ config AUTOFDO_CLANG > > If unsure, say N. > > +config ARCH_SUPPORTS_PROPELLER_CLANG > + bool > + > +config PROPELLER_CLANG > + bool "Enable Clang's Propeller build" > + depends on ARCH_SUPPORTS_PROPELLER_CLANG > + depends on AUTOFDO_CLANG > + depends on CC_IS_CLANG && CLANG_VERSION >= 190000 CC_IS_CLANG is redundant, but I am fine if you want to have it explicitly. > + help > + This option enables Clang’s Propeller build which > + is on top of AutoFDO build. When the Propeller profiles > + is specified in variable CLANG_PROPELLER_PROFILE_PREFIX > + during the build process, Clang uses the profiles to > + optimize the kernel. > + > + If no profile is specified, Proepller options are "Proepller" is a typo. > + still passed to Clang to facilitate the collection > + of perf data for creating the Propeller profiles in > + subsequent builds. > + > + If unsure, say N. > + > config ARCH_SUPPORTS_CFI_CLANG > bool > help > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 503a0268155a..da47164bfddc 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -127,6 +127,7 @@ config X86 > select ARCH_SUPPORTS_LTO_CLANG_THIN > select ARCH_SUPPORTS_RT > select ARCH_SUPPORTS_AUTOFDO_CLANG > + select ARCH_SUPPORTS_PROPELLER_CLANG if X86_64 > select ARCH_USE_BUILTIN_BSWAP > select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64 > select ARCH_USE_MEMTEST > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S > index 6726be89b7a6..7ecc21c569be 100644 > --- a/arch/x86/kernel/vmlinux.lds.S > +++ b/arch/x86/kernel/vmlinux.lds.S > @@ -442,6 +442,10 @@ SECTIONS > > STABS_DEBUG > DWARF_DEBUG > +#ifdef CONFIG_PROPELLER_CLANG > + .llvm_bb_addr_map : { *(.llvm_bb_addr_map) } > +#endif > + > ELF_DETAILS > > DISCARDS > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index 20e46c0917db..5986dd4cfb14 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -95,14 +95,14 @@ > * With LTO_CLANG, the linker also splits sections by default, so we need > * these macros to combine the sections during the final link. > * > - * With LTO_CLANG, the linker also splits sections by default, so we need > - * these macros to combine the sections during the final link. > + * CONFIG_AUTOFD_CLANG and CONFIG_PROPELLER_CLANG will also split text sections > + * and cluster them in the linking time. > * > * RODATA_MAIN is not used because existing code already defines .rodata.x > * sections to be brought in with rodata. > */ > #if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \ > -defined(CONFIG_AUTOFDO_CLANG) > +defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) If you have "depends on PROPELLER_CLANG" in Kconfig, you do not need to touch this line. When CONFIG_PROPELLER_CLANG is enabled, CONFIG_AUTOFDO_CLANG is already defined. > #define TEXT_MAIN .text .text.[0-9a-zA-Z_]* > #else > #define TEXT_MAIN .text > @@ -556,7 +556,7 @@ defined(CONFIG_AUTOFDO_CLANG) > __cpuidle_text_end = .; \ > __noinstr_text_end = .; > > -#ifdef CONFIG_AUTOFDO_CLANG > +#if defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) Ditto. > #define TEXT_HOT \ > __hot_text_start = .; \ > *(.text.hot .text.hot.*) \ > @@ -584,7 +584,7 @@ defined(CONFIG_AUTOFDO_CLANG) > * first when in these builds. > */ > #if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \ > -defined(CONFIG_AUTOFDO_CLANG) > +defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) Ditto. Make sense only when CONFIG_AUTOFDO_CLANG and CONFIG_PROPELLER_CLANG are independent of each other. > #define TEXT_TEXT \ > ALIGN_FUNCTION(); \ > *(.text.asan.* .text.tsan.*) \ > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib > index e85d6ac31bd9..60354c476956 100644 > --- a/scripts/Makefile.lib > +++ b/scripts/Makefile.lib > @@ -201,6 +201,16 @@ _c_flags += $(if $(patsubst n%,, \ > $(CFLAGS_AUTOFDO_CLANG)) > endif > > +# > +# Enable Clang's Propeller build flags for a file or directory depending on > +# variables AUTOFDO_PROPELLER_obj.o and PROPELLER_PROFILE. The same comment as in 1/6. > +# > +ifeq ($(CONFIG_PROPELLER_CLANG),y) ifdef CONFIG_PROPELLER_CLANG would be simpler, as you used this style in scripts/Makefile.propeller > +_c_flags += $(if $(patsubst n%,, \ > + $(AUTOFDO_PROFILE_$(target-stem).o)$(AUTOFDO_PROFILE)$(PROPELLER_PROFILE))$(is-kernel-object), \ > + $(CFLAGS_PROPELLER_CLANG)) > +endif > + > # $(src) for including checkin headers from generated source files > # $(obj) for including generated headers from checkin source files > ifeq ($(KBUILD_EXTMOD),) > diff --git a/scripts/Makefile.propeller b/scripts/Makefile.propeller > new file mode 100644 > index 000000000000..344190717e47 > --- /dev/null > +++ b/scripts/Makefile.propeller > +# Propeller requires debug information to embed module names in the profiles. > +# If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. Skip this for AutoFDO, > +# as the option should already be set. > +ifndef CONFIG_DEBUG_INFO > + ifndef CONFIG_AUTOFDO_CLANG > + CFLAGS_PROPELLER_CLANG += -gmlt > + endif > +endif This block is dead code due to "depends on AUTOFDO_CLANG". "ifndef CONFIG_AUTOFDO_CLANG" is never met here.
On Sun, Oct 20, 2024 at 10:49 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > Please remove the period at the end of the commit subject. Will fix this. > > > > On Tue, Oct 15, 2024 at 6:34 AM Rong Xu <xur@google.com> wrote: > > > > Add the build support for using Clang's Propeller optimizer. Like > > AutoFDO, Propeller uses hardware sampling to gather information > > about the frequency of execution of different code paths within a > > binary. This information is then used to guide the compiler's > > optimization decisions, resulting in a more efficient binary. > > > > The support requires a Clang compiler LLVM 19 or later, and the > > create_llvm_prof tool > > (https://github.com/google/autofdo/releases/tag/v0.30.1). This > > submission is limited to x86 platforms that support PMU features > > > "This submission" -> "This commit" Will fix this. > > > > > like LBR on Intel machines and AMD Zen3 BRS. > > > > For Arm, we plan to send patches for SPE-based Propeller when > > AutoFDO for Arm is ready. > > > "we plan to send ..." is not a good description once it is committed. > > This sentence should be moved to the cover letter, or reworked. We will move this sentence to the cover letter. > > > > > > > > > > Here is an example workflow for building an AutoFDO+Propeller > > optimized kernel: > > > > 1) Build the kernel on the HOST machine, with AutoFDO and Propeller > > > Why is the "HOST" capitalized? We will fix this. > > > > > build config > > CONFIG_AUTOFDO_CLANG=y > > CONFIG_PROPELLER_CLANG=y > > then > > $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile> > > > > “<autofdo_profile>” is the profile collected when doing a non-Propeller > > AutoFDO build. This step builds a kernel that has the same optimization > > level as AutoFDO, plus a metadata section that records basic block > > information. This kernel image runs as fast as an AutoFDO optimized > > kernel. > > > > 2) Install the kernel on test/production machines. > > > > 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: > > The supported system are: Zen3 with BRS, or Zen4 with amd_lbr_v2 > > # To see if Zen3 support LBR: > > $ cat proc/cpuinfo | grep " brs" > > # To see if Zen4 support LBR: > > $ cat proc/cpuinfo | grep amd_lbr_v2 > > # If the result is yes, then collect the profile using: > > $ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a \ > > -N -b -c <count> -o <perf_file> -- <loadtest> > > > > 4) (Optional) Download the raw perf file to the HOST machine. > > > Same question as above. Will use "host". > > > > > > 5) Generate Propeller profile: > > $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> \ > > --format=propeller --propeller_output_module_name \ > > --out=<propeller_profile_prefix>_cc_profile.txt \ > > --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt > > > > “create_llvm_prof” is the profile conversion tool, and a prebuilt > > binary for linux can be found on > > https://github.com/google/autofdo/releases/tag/v0.30.1 (can also build > > from source). > > > > "<propeller_profile_prefix>" can be something like > > "/home/user/dir/any_string". > > > > This command generates a pair of Propeller profiles: > > "<propeller_profile_prefix>_cc_profile.txt" and > > "<propeller_profile_prefix>_ld_profile.txt". > > > > 6) Rebuild the kernel using the AutoFDO and Propeller profile files. > > CONFIG_AUTOFDO_CLANG=y > > CONFIG_PROPELLER_CLANG=y > > and > > $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile> \ > > CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix> > > > > Co-developed-by: Han Shen <shenhan@google.com> > > Signed-off-by: Han Shen <shenhan@google.com> > > Signed-off-by: Rong Xu <xur@google.com> > > Suggested-by: Sriraman Tallam <tmsriram@google.com> > > Suggested-by: Krzysztof Pszeniczny <kpszeniczny@google.com> > > Suggested-by: Nick Desaulniers <ndesaulniers@google.com> > > Suggested-by: Stephane Eranian <eranian@google.com> > > > > > > > .. only:: subproject and html > > diff --git a/Documentation/dev-tools/propeller.rst b/Documentation/dev-tools/propeller.rst > > new file mode 100644 > > index 000000000000..a217354e0f95 > > --- /dev/null > > +++ b/Documentation/dev-tools/propeller.rst > > @@ -0,0 +1,161 @@ > > +.. SPDX-License-Identifier: GPL-2.0 > > + > > +===================================== > > +Using Propeller with the Linux kernel > > +===================================== > > + > > +This enables Propeller build support for the kernel when using Clang > > +compiler. Propeller is a profile-guided optimization (PGO) method used > > +to optimize binary executables. Like AutoFDO, it utilizes hardware > > +sampling to gather information about the frequency of execution of > > +different code paths within a binary. Unlike AutoFDO, this information > > +is then used right before linking phase to optimize (among others) > > +block layout within and across functions. > > + > > +A few important notes about adopting Propeller optimization: > > + > > +#. Although it can be used as a standalone optimization step, it is > > + strongly recommended to apply Propeller on top of AutoFDO, > > + AutoFDO+ThinLTO or Instrument FDO. The rest of this document > > + assumes this paradigm. > > This is a hard requirement instead of a recommendation > because PROPERLLER_CLANG has "depends on AUTOFDO_CLANG". Actually PROPELLER_CLANG does not depend on AUTOFDO_CLANG. We should apply Propeller on top of the vanilla build kernel. I admit that we did not do a good job to separate these two in this patch. > > > > > > + > > +#. Propeller uses another round of profiling on top of > > + AutoFDO/AutoFDO+ThinLTO/iFDO. The whole build process involves > > + "build-afdo - train-afdo - build-propeller - train-propeller - > > + build-optimized". > > + > > +#. Propeller requires LLVM 19 release or later for Clang/Clang++ > > + and the linker(ld.lld). > > + > > +#. In addition to LLVM toolchain, Propeller requires a profiling > > + conversion tool: https://github.com/google/autofdo with a release > > + after v0.30.1: https://github.com/google/autofdo/releases/tag/v0.30.1. > > + > > +The Propeller optimization process involves the following steps: > > + > > +#. Initial building: Build the AutoFDO or AutoFDO+ThinLTO binary as > > + you would normally do, but with a set of compile-time / link-time > > + flags, so that a special metadata section is created within the > > + kernel binary. The special section is only intend to be used by the > > + profiling tool, it is not part of the runtime image, nor does it > > + change kernel run time text sections. > > + > > +#. 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. Propeller is most effective on > > + platforms supporting advanced PMU features like LBR on Intel > > + machines. This step is the same as profiling the kernel for AutoFDO > > + (the exact perf parameters can be different). > > + > > +#. Propeller profile generation: Perf output file is converted to a > > + pair of Propeller profiles via an offline tool. > > + > > +#. Optimized build: Build the AutoFDO or AutoFDO+ThinLTO optimized > > + binary as you would normally do, but with a compile-time / > > + link-time flag to pick up the Propeller compile time and link time > > + profiles. This build step uses 3 profiles - the AutoFDO profile, > > + the Propeller compile-time profile and the Propeller link-time > > + profile. > > + > > +#. Deployment: The optimized kernel binary is deployed and used > > + in production environments, providing improved performance > > + and reduced latency. > > + > > +Preparation > > +=========== > > + > > +Configure the kernel with:: > > + > > + CONFIG_AUTOFDO_CLANG=y > > > This is automatically met due to "depends on AUTOFDO_CLANG". Agreed. But we will remove the dependency from PROPELlER_CLANG to AUTOFDO_CLANG. So we will keep the part. > > > > > + CONFIG_PROPELLER_CLANG=y > > + > > +Customization > > +============= > > + > > +You can enable or disable Propeller build for individual file and > > +directories by adding a line similar to the following to the > > +respective kernel Makefile: > > The same comment as in 1/6. We will fix this similar to the proposed change in 1/6 if you think the change there is acceptable. > > > > > +- For enabling a single file (e.g. foo.o):: > > + > > + PROPELLER_PROFILE_foo.o := y > > + > > +- For enabling all files in one directory:: > > + > > + PROPELLER_PROFILE := y > > + > > +- For disabling one file:: > > + > > + PROPELLER_PROFILE_foo.o := n > > + > > +- For disabling all files in one directory:: > > + > > + PROPELLER__PROFILE := n > > + > > + > > +Workflow > > +======== > > + > > +Here is an example workflow for building an AutoFDO+Propeller kernel: > > + > > +1) Assuming an AutoFDO profile is already collected following > > + instructions in the AutoFDO document, build the kernel on the HOST > > + machine, with AutoFDO and Propeller build configs :: > > + > > + CONFIG_AUTOFDO_CLANG=y > > + CONFIG_PROPELLER_CLANG=y > > + > > + and :: > > + > > + $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo-profile-name> > > + > > +2) Install the kernel on the TEST machine. > > > I am repeatedly encountered with capitalized "HOST" and "TEST". > > Does this term have a special meaning instead of a test machine in general? No special meaning. This is not intentional. Will fix this. > > > > > > > > > + > > +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:: > > + > > + $ perf record --pfm-event RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c <count> -o <perf_file> -- <loadtest> > > + > > + Note you can repeat the above steps to collect multiple <perf_file>s. > > + > > +4) (Optional) Download the raw perf file(s) to the HOST machine. > > + > > +5) Use the create_llvm_prof tool (https://github.com/google/autofdo) to > > + generate Propeller profile. :: > > + > > + $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> > > + --format=propeller --propeller_output_module_name > > + --out=<propeller_profile_prefix>_cc_profile.txt > > + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt > > + > > + "<propeller_profile_prefix>" can be something like "/home/user/dir/any_string". > > + > > + This command generates a pair of Propeller profiles: > > + "<propeller_profile_prefix>_cc_profile.txt" and > > + "<propeller_profile_prefix>_ld_profile.txt". > > + > > + If there are more than 1 perf_file collected in the previous step, > > + you can create a temp list file "<perf_file_list>" with each line > > + containing one perf file name and run:: > > + > > + $ create_llvm_prof --binary=<vmlinux> --profile=@<perf_file_list> > > + --format=propeller --propeller_output_module_name > > + --out=<propeller_profile_prefix>_cc_profile.txt > > + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt > > + > > +6) Rebuild the kernel using the AutoFDO and Propeller > > + profiles. :: > > > "." and "::" are an odd combination. "::" is an rst marker. I will make sure the rendered text looks good. > > > > > > + > > + CONFIG_AUTOFDO_CLANG=y > > + CONFIG_PROPELLER_CLANG=y > > + > > + and :: > > + > > + $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<profile_file> CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix> > > > > > diff --git a/Makefile b/Makefile > > index bbb6ec68f5dc..2d2f688c21c6 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -1019,6 +1019,7 @@ include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan > > include-$(CONFIG_KCOV) += scripts/Makefile.kcov > > include-$(CONFIG_RANDSTRUCT) += scripts/Makefile.randstruct > > include-$(CONFIG_AUTOFDO_CLANG) += scripts/Makefile.autofdo > > +include-$(CONFIG_PROPELLER_CLANG) += scripts/Makefile.propeller > > include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins > > > > include $(addprefix $(srctree)/, $(include-y)) > > diff --git a/arch/Kconfig b/arch/Kconfig > > index 5e9604960cbb..fdeb5f173a10 100644 > > --- a/arch/Kconfig > > +++ b/arch/Kconfig > > @@ -831,6 +831,28 @@ config AUTOFDO_CLANG > > > > If unsure, say N. > > > > +config ARCH_SUPPORTS_PROPELLER_CLANG > > + bool > > + > > +config PROPELLER_CLANG > > + bool "Enable Clang's Propeller build" > > + depends on ARCH_SUPPORTS_PROPELLER_CLANG > > + depends on AUTOFDO_CLANG > > + depends on CC_IS_CLANG && CLANG_VERSION >= 190000 > > > CC_IS_CLANG is redundant, but I am fine if you want to have it explicitly. Let's keep this just for clarity purposes. > > > > > + help > > + This option enables Clang’s Propeller build which > > + is on top of AutoFDO build. When the Propeller profiles > > + is specified in variable CLANG_PROPELLER_PROFILE_PREFIX > > + during the build process, Clang uses the profiles to > > + optimize the kernel. > > + > > + If no profile is specified, Proepller options are > > > "Proepller" is a typo. Thanks! Will fix this. > > > > > > + still passed to Clang to facilitate the collection > > + of perf data for creating the Propeller profiles in > > + subsequent builds. > > + > > + If unsure, say N. > > + > > config ARCH_SUPPORTS_CFI_CLANG > > bool > > help > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > > index 503a0268155a..da47164bfddc 100644 > > --- a/arch/x86/Kconfig > > +++ b/arch/x86/Kconfig > > @@ -127,6 +127,7 @@ config X86 > > select ARCH_SUPPORTS_LTO_CLANG_THIN > > select ARCH_SUPPORTS_RT > > select ARCH_SUPPORTS_AUTOFDO_CLANG > > + select ARCH_SUPPORTS_PROPELLER_CLANG if X86_64 > > select ARCH_USE_BUILTIN_BSWAP > > select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64 > > select ARCH_USE_MEMTEST > > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S > > index 6726be89b7a6..7ecc21c569be 100644 > > --- a/arch/x86/kernel/vmlinux.lds.S > > +++ b/arch/x86/kernel/vmlinux.lds.S > > @@ -442,6 +442,10 @@ SECTIONS > > > > STABS_DEBUG > > DWARF_DEBUG > > +#ifdef CONFIG_PROPELLER_CLANG > > + .llvm_bb_addr_map : { *(.llvm_bb_addr_map) } > > +#endif > > + > > ELF_DETAILS > > > > DISCARDS > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > > index 20e46c0917db..5986dd4cfb14 100644 > > --- a/include/asm-generic/vmlinux.lds.h > > +++ b/include/asm-generic/vmlinux.lds.h > > @@ -95,14 +95,14 @@ > > * With LTO_CLANG, the linker also splits sections by default, so we need > > * these macros to combine the sections during the final link. > > * > > - * With LTO_CLANG, the linker also splits sections by default, so we need > > - * these macros to combine the sections during the final link. > > + * CONFIG_AUTOFD_CLANG and CONFIG_PROPELLER_CLANG will also split text sections > > + * and cluster them in the linking time. > > * > > * RODATA_MAIN is not used because existing code already defines .rodata.x > > * sections to be brought in with rodata. > > */ > > #if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \ > > -defined(CONFIG_AUTOFDO_CLANG) > > +defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) > > > If you have "depends on PROPELLER_CLANG" in Kconfig, > you do not need to touch this line. > > When CONFIG_PROPELLER_CLANG is enabled, CONFIG_AUTOFDO_CLANG is already defined. We will remove the dependency from CONFIG_PROPELLER_CLANG to CONFIG_AUTOFDO_CLANG. So I guess we will keep this part. > > > > > > #define TEXT_MAIN .text .text.[0-9a-zA-Z_]* > > #else > > #define TEXT_MAIN .text > > @@ -556,7 +556,7 @@ defined(CONFIG_AUTOFDO_CLANG) > > __cpuidle_text_end = .; \ > > __noinstr_text_end = .; > > > > -#ifdef CONFIG_AUTOFDO_CLANG > > +#if defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) > > > Ditto. > > > > #define TEXT_HOT \ > > __hot_text_start = .; \ > > *(.text.hot .text.hot.*) \ > > @@ -584,7 +584,7 @@ defined(CONFIG_AUTOFDO_CLANG) > > * first when in these builds. > > */ > > #if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \ > > -defined(CONFIG_AUTOFDO_CLANG) > > +defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) > > > Ditto. > Make sense only when CONFIG_AUTOFDO_CLANG and CONFIG_PROPELLER_CLANG > are independent of each other. We will make CONFIG_AUTOFDO_CLANG and CONFIG_PROPELLER_CLANG independent of each other. > > > > > #define TEXT_TEXT \ > > ALIGN_FUNCTION(); \ > > *(.text.asan.* .text.tsan.*) \ > > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib > > index e85d6ac31bd9..60354c476956 100644 > > --- a/scripts/Makefile.lib > > +++ b/scripts/Makefile.lib > > @@ -201,6 +201,16 @@ _c_flags += $(if $(patsubst n%,, \ > > $(CFLAGS_AUTOFDO_CLANG)) > > endif > > > > +# > > +# Enable Clang's Propeller build flags for a file or directory depending on > > +# variables AUTOFDO_PROPELLER_obj.o and PROPELLER_PROFILE. > > The same comment as in 1/6. Will fix this. > > > > > +# > > +ifeq ($(CONFIG_PROPELLER_CLANG),y) > > > > ifdef CONFIG_PROPELLER_CLANG > > would be simpler, as you used this style in scripts/Makefile.propeller Will use the suggested code. > > > > > > > > +_c_flags += $(if $(patsubst n%,, \ > > + $(AUTOFDO_PROFILE_$(target-stem).o)$(AUTOFDO_PROFILE)$(PROPELLER_PROFILE))$(is-kernel-object), \ > > + $(CFLAGS_PROPELLER_CLANG)) > > +endif > > + > > # $(src) for including checkin headers from generated source files > > # $(obj) for including generated headers from checkin source files > > ifeq ($(KBUILD_EXTMOD),) > > diff --git a/scripts/Makefile.propeller b/scripts/Makefile.propeller > > new file mode 100644 > > index 000000000000..344190717e47 > > --- /dev/null > > +++ b/scripts/Makefile.propeller > > > > +# Propeller requires debug information to embed module names in the profiles. > > +# If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. Skip this for AutoFDO, > > +# as the option should already be set. > > +ifndef CONFIG_DEBUG_INFO > > + ifndef CONFIG_AUTOFDO_CLANG > > + CFLAGS_PROPELLER_CLANG += -gmlt > > + endif > > +endif > > > This block is dead code due to "depends on AUTOFDO_CLANG". > > "ifndef CONFIG_AUTOFDO_CLANG" is never met here. Yes. I think we still need to when we remove the dependency to CONFIG_AUTOFDO_CLANG. > > > > > > > > -- > Best Regards > Masahiro Yamada
On Tue, Oct 22, 2024 at 9:00 AM Rong Xu <xur@google.com> wrote: > > > +=========== > > > + > > > +Configure the kernel with:: > > > + > > > + CONFIG_AUTOFDO_CLANG=y > > > > > > This is automatically met due to "depends on AUTOFDO_CLANG". > > Agreed. But we will remove the dependency from PROPELlER_CLANG to AUTOFDO_CLANG. > So we will keep the part. You can replace "depends on AUTOFDO_CLANG" with "imply AUTOFDO_CLANG" if it is sensible. Up to you. -- Best Regards Masahiro Yamada
On Wed, Oct 23, 2024, at 07:06, Masahiro Yamada wrote: > On Tue, Oct 22, 2024 at 9:00 AM Rong Xu <xur@google.com> wrote: > >> > > +=========== >> > > + >> > > +Configure the kernel with:: >> > > + >> > > + CONFIG_AUTOFDO_CLANG=y >> > >> > >> > This is automatically met due to "depends on AUTOFDO_CLANG". >> >> Agreed. But we will remove the dependency from PROPELlER_CLANG to AUTOFDO_CLANG. >> So we will keep the part. > > > You can replace "depends on AUTOFDO_CLANG" with > "imply AUTOFDO_CLANG" if it is sensible. > > Up to you. I don't think we should ever encourage the use of 'imply' because it is almost always used incorrectly. Arnd
On Wed, Oct 23, 2024 at 4:25 PM Arnd Bergmann <arnd@arndb.de> wrote: > > On Wed, Oct 23, 2024, at 07:06, Masahiro Yamada wrote: > > On Tue, Oct 22, 2024 at 9:00 AM Rong Xu <xur@google.com> wrote: > > > >> > > +=========== > >> > > + > >> > > +Configure the kernel with:: > >> > > + > >> > > + CONFIG_AUTOFDO_CLANG=y > >> > > >> > > >> > This is automatically met due to "depends on AUTOFDO_CLANG". > >> > >> Agreed. But we will remove the dependency from PROPELlER_CLANG to AUTOFDO_CLANG. > >> So we will keep the part. > > > > > > You can replace "depends on AUTOFDO_CLANG" with > > "imply AUTOFDO_CLANG" if it is sensible. > > > > Up to you. > > I don't think we should ever encourage the use of 'imply' > because it is almost always used incorrectly. If we are able to delete the 'imply' keyword, Kconfig would be a bit cleaner. In most cases, it can be replaced with 'default'.
While Propeller often works best with AutoFDO (or the instrumentation based FDO), it's not required. One can use Propeller (or similar post-link-optimizer, like Bolt) on plain kernel builds. So I will remove "depends on AUTOFDO_CLANG". I will not use "imply" -- simpler is better here. -Rong On Wed, Oct 23, 2024 at 12:29 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > On Wed, Oct 23, 2024 at 4:25 PM Arnd Bergmann <arnd@arndb.de> wrote: > > > > On Wed, Oct 23, 2024, at 07:06, Masahiro Yamada wrote: > > > On Tue, Oct 22, 2024 at 9:00 AM Rong Xu <xur@google.com> wrote: > > > > > >> > > +=========== > > >> > > + > > >> > > +Configure the kernel with:: > > >> > > + > > >> > > + CONFIG_AUTOFDO_CLANG=y > > >> > > > >> > > > >> > This is automatically met due to "depends on AUTOFDO_CLANG". > > >> > > >> Agreed. But we will remove the dependency from PROPELlER_CLANG to AUTOFDO_CLANG. > > >> So we will keep the part. > > > > > > > > > You can replace "depends on AUTOFDO_CLANG" with > > > "imply AUTOFDO_CLANG" if it is sensible. > > > > > > Up to you. > > > > I don't think we should ever encourage the use of 'imply' > > because it is almost always used incorrectly. > > If we are able to delete the 'imply' keyword, Kconfig would be a bit cleaner. > > In most cases, it can be replaced with 'default'. > > > > -- > Best Regards > Masahiro Yamada
diff --git a/Documentation/dev-tools/index.rst b/Documentation/dev-tools/index.rst index 6945644f7008..3c0ac08b2709 100644 --- a/Documentation/dev-tools/index.rst +++ b/Documentation/dev-tools/index.rst @@ -35,6 +35,7 @@ Documentation/dev-tools/testing-overview.rst checkuapi gpio-sloppy-logic-analyzer autofdo + propeller .. only:: subproject and html diff --git a/Documentation/dev-tools/propeller.rst b/Documentation/dev-tools/propeller.rst new file mode 100644 index 000000000000..a217354e0f95 --- /dev/null +++ b/Documentation/dev-tools/propeller.rst @@ -0,0 +1,161 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================================== +Using Propeller with the Linux kernel +===================================== + +This enables Propeller build support for the kernel when using Clang +compiler. Propeller is a profile-guided optimization (PGO) method used +to optimize binary executables. Like AutoFDO, it utilizes hardware +sampling to gather information about the frequency of execution of +different code paths within a binary. Unlike AutoFDO, this information +is then used right before linking phase to optimize (among others) +block layout within and across functions. + +A few important notes about adopting Propeller optimization: + +#. Although it can be used as a standalone optimization step, it is + strongly recommended to apply Propeller on top of AutoFDO, + AutoFDO+ThinLTO or Instrument FDO. The rest of this document + assumes this paradigm. + +#. Propeller uses another round of profiling on top of + AutoFDO/AutoFDO+ThinLTO/iFDO. The whole build process involves + "build-afdo - train-afdo - build-propeller - train-propeller - + build-optimized". + +#. Propeller requires LLVM 19 release or later for Clang/Clang++ + and the linker(ld.lld). + +#. In addition to LLVM toolchain, Propeller requires a profiling + conversion tool: https://github.com/google/autofdo with a release + after v0.30.1: https://github.com/google/autofdo/releases/tag/v0.30.1. + +The Propeller optimization process involves the following steps: + +#. Initial building: Build the AutoFDO or AutoFDO+ThinLTO binary as + you would normally do, but with a set of compile-time / link-time + flags, so that a special metadata section is created within the + kernel binary. The special section is only intend to be used by the + profiling tool, it is not part of the runtime image, nor does it + change kernel run time text sections. + +#. 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. Propeller is most effective on + platforms supporting advanced PMU features like LBR on Intel + machines. This step is the same as profiling the kernel for AutoFDO + (the exact perf parameters can be different). + +#. Propeller profile generation: Perf output file is converted to a + pair of Propeller profiles via an offline tool. + +#. Optimized build: Build the AutoFDO or AutoFDO+ThinLTO optimized + binary as you would normally do, but with a compile-time / + link-time flag to pick up the Propeller compile time and link time + profiles. This build step uses 3 profiles - the AutoFDO profile, + the Propeller compile-time profile and the Propeller link-time + profile. + +#. Deployment: The optimized kernel binary is deployed and used + in production environments, providing improved performance + and reduced latency. + +Preparation +=========== + +Configure the kernel with:: + + CONFIG_AUTOFDO_CLANG=y + CONFIG_PROPELLER_CLANG=y + +Customization +============= + +You can enable or disable Propeller build for individual file and +directories by adding a line similar to the following to the +respective kernel Makefile: + +- For enabling a single file (e.g. foo.o):: + + PROPELLER_PROFILE_foo.o := y + +- For enabling all files in one directory:: + + PROPELLER_PROFILE := y + +- For disabling one file:: + + PROPELLER_PROFILE_foo.o := n + +- For disabling all files in one directory:: + + PROPELLER__PROFILE := n + + +Workflow +======== + +Here is an example workflow for building an AutoFDO+Propeller kernel: + +1) Assuming an AutoFDO profile is already collected following + instructions in the AutoFDO document, build the kernel on the HOST + machine, with AutoFDO and Propeller build configs :: + + CONFIG_AUTOFDO_CLANG=y + CONFIG_PROPELLER_CLANG=y + + and :: + + $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo-profile-name> + +2) Install the kernel on the TEST machine. + +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:: + + $ perf record --pfm-event RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c <count> -o <perf_file> -- <loadtest> + + Note you can repeat the above steps to collect multiple <perf_file>s. + +4) (Optional) Download the raw perf file(s) to the HOST machine. + +5) Use the create_llvm_prof tool (https://github.com/google/autofdo) to + generate Propeller profile. :: + + $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> + --format=propeller --propeller_output_module_name + --out=<propeller_profile_prefix>_cc_profile.txt + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt + + "<propeller_profile_prefix>" can be something like "/home/user/dir/any_string". + + This command generates a pair of Propeller profiles: + "<propeller_profile_prefix>_cc_profile.txt" and + "<propeller_profile_prefix>_ld_profile.txt". + + If there are more than 1 perf_file collected in the previous step, + you can create a temp list file "<perf_file_list>" with each line + containing one perf file name and run:: + + $ create_llvm_prof --binary=<vmlinux> --profile=@<perf_file_list> + --format=propeller --propeller_output_module_name + --out=<propeller_profile_prefix>_cc_profile.txt + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt + +6) Rebuild the kernel using the AutoFDO and Propeller + profiles. :: + + CONFIG_AUTOFDO_CLANG=y + CONFIG_PROPELLER_CLANG=y + + and :: + + $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<profile_file> CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix> diff --git a/MAINTAINERS b/MAINTAINERS index 1b8db863031f..f4cc6dd6c4d8 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -18560,6 +18560,13 @@ S: Maintained F: include/linux/psi* F: kernel/sched/psi.c +PROPELLER BUILD +M: Rong Xu <xur@google.com> +M: Han Shen <shenhan@google.com> +S: Supported +F: Documentation/dev-tools/propeller.rst +F: scripts/Makefile.propeller + PRINTK M: Petr Mladek <pmladek@suse.com> R: Steven Rostedt <rostedt@goodmis.org> diff --git a/Makefile b/Makefile index bbb6ec68f5dc..2d2f688c21c6 100644 --- a/Makefile +++ b/Makefile @@ -1019,6 +1019,7 @@ include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan include-$(CONFIG_KCOV) += scripts/Makefile.kcov include-$(CONFIG_RANDSTRUCT) += scripts/Makefile.randstruct include-$(CONFIG_AUTOFDO_CLANG) += scripts/Makefile.autofdo +include-$(CONFIG_PROPELLER_CLANG) += scripts/Makefile.propeller include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins include $(addprefix $(srctree)/, $(include-y)) diff --git a/arch/Kconfig b/arch/Kconfig index 5e9604960cbb..fdeb5f173a10 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -831,6 +831,28 @@ config AUTOFDO_CLANG If unsure, say N. +config ARCH_SUPPORTS_PROPELLER_CLANG + bool + +config PROPELLER_CLANG + bool "Enable Clang's Propeller build" + depends on ARCH_SUPPORTS_PROPELLER_CLANG + depends on AUTOFDO_CLANG + depends on CC_IS_CLANG && CLANG_VERSION >= 190000 + help + This option enables Clang’s Propeller build which + is on top of AutoFDO build. When the Propeller profiles + is specified in variable CLANG_PROPELLER_PROFILE_PREFIX + during the build process, Clang uses the profiles to + optimize the kernel. + + If no profile is specified, Proepller options are + still passed to Clang to facilitate the collection + of perf data for creating the Propeller profiles in + subsequent builds. + + If unsure, say N. + config ARCH_SUPPORTS_CFI_CLANG bool help diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 503a0268155a..da47164bfddc 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -127,6 +127,7 @@ config X86 select ARCH_SUPPORTS_LTO_CLANG_THIN select ARCH_SUPPORTS_RT select ARCH_SUPPORTS_AUTOFDO_CLANG + select ARCH_SUPPORTS_PROPELLER_CLANG if X86_64 select ARCH_USE_BUILTIN_BSWAP select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64 select ARCH_USE_MEMTEST diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 6726be89b7a6..7ecc21c569be 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -442,6 +442,10 @@ SECTIONS STABS_DEBUG DWARF_DEBUG +#ifdef CONFIG_PROPELLER_CLANG + .llvm_bb_addr_map : { *(.llvm_bb_addr_map) } +#endif + ELF_DETAILS DISCARDS diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 20e46c0917db..5986dd4cfb14 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -95,14 +95,14 @@ * With LTO_CLANG, the linker also splits sections by default, so we need * these macros to combine the sections during the final link. * - * With LTO_CLANG, the linker also splits sections by default, so we need - * these macros to combine the sections during the final link. + * CONFIG_AUTOFD_CLANG and CONFIG_PROPELLER_CLANG will also split text sections + * and cluster them in the linking time. * * RODATA_MAIN is not used because existing code already defines .rodata.x * sections to be brought in with rodata. */ #if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \ -defined(CONFIG_AUTOFDO_CLANG) +defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) #define TEXT_MAIN .text .text.[0-9a-zA-Z_]* #else #define TEXT_MAIN .text @@ -556,7 +556,7 @@ defined(CONFIG_AUTOFDO_CLANG) __cpuidle_text_end = .; \ __noinstr_text_end = .; -#ifdef CONFIG_AUTOFDO_CLANG +#if defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) #define TEXT_HOT \ __hot_text_start = .; \ *(.text.hot .text.hot.*) \ @@ -584,7 +584,7 @@ defined(CONFIG_AUTOFDO_CLANG) * first when in these builds. */ #if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \ -defined(CONFIG_AUTOFDO_CLANG) +defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) #define TEXT_TEXT \ ALIGN_FUNCTION(); \ *(.text.asan.* .text.tsan.*) \ diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index e85d6ac31bd9..60354c476956 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -201,6 +201,16 @@ _c_flags += $(if $(patsubst n%,, \ $(CFLAGS_AUTOFDO_CLANG)) endif +# +# Enable Clang's Propeller build flags for a file or directory depending on +# variables AUTOFDO_PROPELLER_obj.o and PROPELLER_PROFILE. +# +ifeq ($(CONFIG_PROPELLER_CLANG),y) +_c_flags += $(if $(patsubst n%,, \ + $(AUTOFDO_PROFILE_$(target-stem).o)$(AUTOFDO_PROFILE)$(PROPELLER_PROFILE))$(is-kernel-object), \ + $(CFLAGS_PROPELLER_CLANG)) +endif + # $(src) for including checkin headers from generated source files # $(obj) for including generated headers from checkin source files ifeq ($(KBUILD_EXTMOD),) diff --git a/scripts/Makefile.propeller b/scripts/Makefile.propeller new file mode 100644 index 000000000000..344190717e47 --- /dev/null +++ b/scripts/Makefile.propeller @@ -0,0 +1,28 @@ +# SPDX-License-Identifier: GPL-2.0 + +# Enable available and selected Clang Propeller features. +ifdef CLANG_PROPELLER_PROFILE_PREFIX + CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=list=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt -ffunction-sections + KBUILD_LDFLAGS += --symbol-ordering-file=$(CLANG_PROPELLER_PROFILE_PREFIX)_ld_profile.txt --no-warn-symbol-ordering +else + CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=labels +endif + +# Propeller requires debug information to embed module names in the profiles. +# If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. Skip this for AutoFDO, +# as the option should already be set. +ifndef CONFIG_DEBUG_INFO + ifndef CONFIG_AUTOFDO_CLANG + CFLAGS_PROPELLER_CLANG += -gmlt + endif +endif + +ifdef CONFIG_LTO_CLANG_THIN + ifdef CLANG_PROPELLER_PROFILE_PREFIX + KBUILD_LDFLAGS += --lto-basic-block-sections=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt + else + KBUILD_LDFLAGS += --lto-basic-block-sections=labels + endif +endif + +export CFLAGS_PROPELLER_CLANG diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 4c5229991e1e..05a0fb4a3d1a 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -4558,6 +4558,7 @@ static int validate_ibt(struct objtool_file *file) !strcmp(sec->name, "__mcount_loc") || !strcmp(sec->name, ".kcfi_traps") || !strcmp(sec->name, ".llvm.call-graph-profile") || + !strcmp(sec->name, ".llvm_bb_addr_map") || strstr(sec->name, "__patchable_function_entries")) continue;
Add the build support for using Clang's Propeller optimizer. Like AutoFDO, Propeller uses hardware sampling to gather information about the frequency of execution of different code paths within a binary. This information is then used to guide the compiler's optimization decisions, resulting in a more efficient binary. The support requires a Clang compiler LLVM 19 or later, and the create_llvm_prof tool (https://github.com/google/autofdo/releases/tag/v0.30.1). This submission is limited to x86 platforms that support PMU features like LBR on Intel machines and AMD Zen3 BRS. For Arm, we plan to send patches for SPE-based Propeller when AutoFDO for Arm is ready. Here is an example workflow for building an AutoFDO+Propeller optimized kernel: 1) Build the kernel on the HOST machine, with AutoFDO and Propeller build config CONFIG_AUTOFDO_CLANG=y CONFIG_PROPELLER_CLANG=y then $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile> “<autofdo_profile>” is the profile collected when doing a non-Propeller AutoFDO build. This step builds a kernel that has the same optimization level as AutoFDO, plus a metadata section that records basic block information. This kernel image runs as fast as an AutoFDO optimized kernel. 2) Install the kernel on test/production machines. 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: The supported system are: Zen3 with BRS, or Zen4 with amd_lbr_v2 # To see if Zen3 support LBR: $ cat proc/cpuinfo | grep " brs" # To see if Zen4 support LBR: $ cat proc/cpuinfo | grep amd_lbr_v2 # If the result is yes, then collect the profile using: $ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a \ -N -b -c <count> -o <perf_file> -- <loadtest> 4) (Optional) Download the raw perf file to the HOST machine. 5) Generate Propeller profile: $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> \ --format=propeller --propeller_output_module_name \ --out=<propeller_profile_prefix>_cc_profile.txt \ --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt “create_llvm_prof” is the profile conversion tool, and a prebuilt binary for linux can be found on https://github.com/google/autofdo/releases/tag/v0.30.1 (can also build from source). "<propeller_profile_prefix>" can be something like "/home/user/dir/any_string". This command generates a pair of Propeller profiles: "<propeller_profile_prefix>_cc_profile.txt" and "<propeller_profile_prefix>_ld_profile.txt". 6) Rebuild the kernel using the AutoFDO and Propeller profile files. CONFIG_AUTOFDO_CLANG=y CONFIG_PROPELLER_CLANG=y and $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile> \ CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix> Co-developed-by: Han Shen <shenhan@google.com> Signed-off-by: Han Shen <shenhan@google.com> Signed-off-by: Rong Xu <xur@google.com> Suggested-by: Sriraman Tallam <tmsriram@google.com> Suggested-by: Krzysztof Pszeniczny <kpszeniczny@google.com> Suggested-by: Nick Desaulniers <ndesaulniers@google.com> Suggested-by: Stephane Eranian <eranian@google.com> --- Documentation/dev-tools/index.rst | 1 + Documentation/dev-tools/propeller.rst | 161 ++++++++++++++++++++++++++ MAINTAINERS | 7 ++ Makefile | 1 + arch/Kconfig | 22 ++++ arch/x86/Kconfig | 1 + arch/x86/kernel/vmlinux.lds.S | 4 + include/asm-generic/vmlinux.lds.h | 10 +- scripts/Makefile.lib | 10 ++ scripts/Makefile.propeller | 28 +++++ tools/objtool/check.c | 1 + 11 files changed, 241 insertions(+), 5 deletions(-) create mode 100644 Documentation/dev-tools/propeller.rst create mode 100644 scripts/Makefile.propeller