Commit-ID: 0b101e62afe626ecae60173f92f1e0ec72151653 Gitweb: http://git.kernel.org/tip/0b101e62afe626ecae60173f92f1e0ec72151653 Author: Denys Vlasenko <[email protected]> AuthorDate: Thu, 24 Sep 2015 14:02:29 +0200 Committer: Ingo Molnar <[email protected]> CommitDate: Fri, 25 Sep 2015 09:44:34 +0200
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 <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/include/asm/processor.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 19577dd..b55f309 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(); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
