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Message-ID: <20241102175115.1769468-7-xur@google.com>
Date: Sat, 2 Nov 2024 10:51:13 -0700
From: Rong Xu <xur@...gle.com>
To: Alice Ryhl <aliceryhl@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>,
Arnd Bergmann <arnd@...db.de>, Bill Wendling <morbo@...gle.com>, Borislav Petkov <bp@...en8.de>,
Breno Leitao <leitao@...ian.org>, Brian Gerst <brgerst@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.com>, David Li <davidxl@...gle.com>,
Han Shen <shenhan@...gle.com>, Heiko Carstens <hca@...ux.ibm.com>, "H. Peter Anvin" <hpa@...or.com>,
Ingo Molnar <mingo@...hat.com>, Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>,
Josh Poimboeuf <jpoimboe@...nel.org>, Juergen Gross <jgross@...e.com>,
Justin Stitt <justinstitt@...gle.com>, Kees Cook <kees@...nel.org>,
Masahiro Yamada <masahiroy@...nel.org>, "Mike Rapoport (IBM)" <rppt@...nel.org>,
Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>,
Nicolas Schier <nicolas@...sle.eu>, "Paul E. McKenney" <paulmck@...nel.org>,
Peter Zijlstra <peterz@...radead.org>, Rong Xu <xur@...gle.com>,
Sami Tolvanen <samitolvanen@...gle.com>, Thomas Gleixner <tglx@...utronix.de>,
Wei Yang <richard.weiyang@...il.com>, workflows@...r.kernel.org,
Miguel Ojeda <miguel.ojeda.sandonis@...il.com>, Maksim Panchenko <max4bolt@...il.com>,
"David S. Miller" <davem@...emloft.net>, Andreas Larsson <andreas@...sler.com>,
Yonghong Song <yonghong.song@...ux.dev>, Yabin Cui <yabinc@...gle.com>,
Krzysztof Pszeniczny <kpszeniczny@...gle.com>, Sriraman Tallam <tmsriram@...gle.com>,
Stephane Eranian <eranian@...gle.com>
Cc: x86@...nel.org, linux-arch@...r.kernel.org, sparclinux@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kbuild@...r.kernel.org,
linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH v7 6/7] AutoFDO: Enable machine function split optimization
for AutoFDO
Enable the machine function split optimization for AutoFDO in Clang.
Machine function split (MFS) is a pass in the Clang compiler that
splits a function into hot and cold parts. The linker groups all
cold blocks across functions together. This decreases hot code
fragmentation and improves iCache and iTLB utilization.
MFS requires a profile so this is enabled only for the AutoFDO builds.
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>
Tested-by: Yonghong Song <yonghong.song@...ux.dev>
Tested-by: Yabin Cui <yabinc@...gle.com>
Tested-by: Nathan Chancellor <nathan@...nel.org>
Reviewed-by: Kees Cook <kees@...nel.org>
---
include/asm-generic/vmlinux.lds.h | 7 ++++++-
scripts/Makefile.autofdo | 2 ++
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index bd64fdedabd2f..8a0bb3946cf05 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -556,6 +556,11 @@ defined(CONFIG_AUTOFDO_CLANG)
__cpuidle_text_end = .; \
__noinstr_text_end = .;
+#define TEXT_SPLIT \
+ __split_text_start = .; \
+ *(.text.split .text.split.[0-9a-zA-Z_]*) \
+ __split_text_end = .;
+
#define TEXT_UNLIKELY \
__unlikely_text_start = .; \
*(.text.unlikely .text.unlikely.*) \
@@ -582,6 +587,7 @@ defined(CONFIG_AUTOFDO_CLANG)
ALIGN_FUNCTION(); \
*(.text.asan.* .text.tsan.*) \
*(.text.unknown .text.unknown.*) \
+ TEXT_SPLIT \
TEXT_UNLIKELY \
. = ALIGN(PAGE_SIZE); \
TEXT_HOT \
@@ -589,7 +595,6 @@ defined(CONFIG_AUTOFDO_CLANG)
NOINSTR_TEXT \
*(.ref.text)
-
/* sched.text is aling to function alignment to secure we have same
* address even at second ld pass when generating System.map */
#define SCHED_TEXT \
diff --git a/scripts/Makefile.autofdo b/scripts/Makefile.autofdo
index 6155d6fc4ca7f..1caf2457e585c 100644
--- a/scripts/Makefile.autofdo
+++ b/scripts/Makefile.autofdo
@@ -10,6 +10,7 @@ endif
ifdef CLANG_AUTOFDO_PROFILE
CFLAGS_AUTOFDO_CLANG += -fprofile-sample-use=$(CLANG_AUTOFDO_PROFILE) -ffunction-sections
+ CFLAGS_AUTOFDO_CLANG += -fsplit-machine-functions
endif
ifdef CONFIG_LTO_CLANG_THIN
@@ -17,6 +18,7 @@ ifdef CONFIG_LTO_CLANG_THIN
KBUILD_LDFLAGS += --lto-sample-profile=$(CLANG_AUTOFDO_PROFILE)
endif
KBUILD_LDFLAGS += --mllvm=-enable-fs-discriminator=true --mllvm=-improved-fs-discriminator=true -plugin-opt=thinlto
+ KBUILD_LDFLAGS += -plugin-opt=-split-machine-functions
endif
export CFLAGS_AUTOFDO_CLANG
--
2.47.0.163.g1226f6d8fa-goog
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