[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAK7LNAQ0Z38a1Nt=_XKT3i-UpauiO9RaZAye6LXGCFzvg2R8Bg@mail.gmail.com>
Date: Sun, 29 Sep 2024 20:08:43 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Rong Xu <xur@...gle.com>
Cc: Han Shen <shenhan@...gle.com>, Sriraman Tallam <tmsriram@...gle.com>,
David Li <davidxl@...gle.com>, Jonathan Corbet <corbet@....net>,
Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>,
Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H . Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>, Arnd Bergmann <arnd@...db.de>,
Josh Poimboeuf <jpoimboe@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>,
Justin Stitt <justinstitt@...gle.com>, Vegard Nossum <vegard.nossum@...cle.com>,
John Moon <john@...on.dev>, Andrew Morton <akpm@...ux-foundation.org>,
Heiko Carstens <hca@...ux.ibm.com>, Luis Chamberlain <mcgrof@...nel.org>,
Samuel Holland <samuel.holland@...ive.com>, Mike Rapoport <rppt@...nel.org>,
"Paul E . McKenney" <paulmck@...nel.org>, Rafael Aquini <aquini@...hat.com>, Petr Pavlu <petr.pavlu@...e.com>,
Eric DeVolder <eric.devolder@...cle.com>, Bjorn Helgaas <bhelgaas@...gle.com>,
Randy Dunlap <rdunlap@...radead.org>, Benjamin Segall <bsegall@...gle.com>,
Breno Leitao <leitao@...ian.org>, Wei Yang <richard.weiyang@...il.com>,
Brian Gerst <brgerst@...il.com>, Juergen Gross <jgross@...e.com>,
Palmer Dabbelt <palmer@...osinc.com>, Alexandre Ghiti <alexghiti@...osinc.com>,
Kees Cook <kees@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>,
Xiao Wang <xiao.w.wang@...el.com>, Jan Kiszka <jan.kiszka@...mens.com>,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-kbuild@...r.kernel.org, linux-efi@...r.kernel.org,
linux-arch@...r.kernel.org, llvm@...ts.linux.dev,
Krzysztof Pszeniczny <kpszeniczny@...gle.com>, Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 6/6] Add Propeller configuration for kernel build.
On Mon, Jul 29, 2024 at 5:31 AM Rong Xu <xur@...gle.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
> 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@...gle.com>
> Signed-off-by: Han Shen <shenhan@...gle.com>
> Signed-off-by: Rong Xu <xur@...gle.com>
> Suggested-by: Sriraman Tallam <tmsriram@...gle.com>
> Suggested-by: Krzysztof Pszeniczny <kpszeniczny@...gle.com>
> Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Suggested-by: Stephane Eranian <eranian@...gle.com>
> ---
> diff --git a/Makefile b/Makefile
> index 5ae30cc94a26..85a96d973f20 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1025,6 +1025,7 @@ include-$(CONFIG_KCOV) += scripts/Makefile.kcov
> include-$(CONFIG_RANDSTRUCT) += scripts/Makefile.randstruct
> include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins
> include-$(CONFIG_AUTOFDO_CLANG) += scripts/Makefile.autofdo
> +include-$(CONFIG_PROPELLER_CLANG) += scripts/Makefile.propeller
Please do not ignore this comment:
https://github.com/torvalds/linux/blob/v6.11/Makefile#L1016
> +ifdef CONFIG_LTO_CLANG
> +ifdef CONFIG_LTO_CLANG_THIN
> +ifdef CLANG_PROPELLER_PROFILE_PREFIX
> +KBUILD_LDFLAGS += --lto-basic-block-sections=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt
> +else
> +KBUILD_LDFLAGS += --lto-basic-block-sections=labels
> +endif
> +endif
> +else
> +endif
Unreadable and redundant.
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
--
Best Regards
Masahiro Yamada
Powered by blists - more mailing lists