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| author | Denys Vlasenko <dvlasenk@redhat.com> | 2015-09-24 14:02:29 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-09-25 09:44:34 +0200 |
| commit | 0b101e62afe626ecae60173f92f1e0ec72151653 (patch) | |
| tree | 94ee05d83ecf4c0d185ef909e502bc3b97d87cdb /arch | |
| parent | 3f2c5085ed99b6ad233cf77009c2f4f898b2f7c8 (diff) | |
| download | lwn-0b101e62afe626ecae60173f92f1e0ec72151653.tar.gz lwn-0b101e62afe626ecae60173f92f1e0ec72151653.zip | |
x86/asm: Force inlining of cpu_relax()
On x86, cpu_relax() simply calls rep_nop(), which generates one
instruction, PAUSE (aka REP NOP).
With this config:
http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os
gcc-4.7.2 does not always inline rep_nop(): it generates several
copies of this:
<rep_nop> (16 copies, 194 calls):
55 push %rbp
48 89 e5 mov %rsp,%rbp
f3 90 pause
5d pop %rbp
c3 retq
See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122
This patch fixes this via s/inline/__always_inline/
on rep_nop() and cpu_relax().
( Forcing inlining only on rep_nop() causes GCC to
deinline cpu_relax(), with almost no change in generated code).
text data bss dec hex filename
88118971 19905208 36421632 144445811 89c1173 vmlinux.before
88118139 19905208 36421632 144444979 89c0e33 vmlinux
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1443096149-27291-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/processor.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 19577dd325fa..b55f30960554 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -556,12 +556,12 @@ static inline unsigned int cpuid_edx(unsigned int op) } /* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */ -static inline void rep_nop(void) +static __always_inline void rep_nop(void) { asm volatile("rep; nop" ::: "memory"); } -static inline void cpu_relax(void) +static __always_inline void cpu_relax(void) { rep_nop(); } |