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ARM: cmpxchg: define __HAVE_ARCH_CMPXCHG for armv6 and later 

Both pi_stress and sigwaittest in rt-test show performance gain with
__HAVE_ARCH_CMPXCHG. Testing result on coretile_express_a9x4:

pi_stress -p 99 --duration=300 (on linux-3.4-rc5; bigger is better)
  vanilla:     Total inversion performed: 5493381
  patched:     Total inversion performed: 5621746

sigwaittest -p 99 -l 100000 (on linux-3.4-rc5-rt6; less is better)
  3.4-rc5-rt6: Min   24, Cur   27, Avg   30, Max   98
  patched:     Min   19, Cur   21, Avg   23, Max   96

Signed-off-by: Yong Zhang <yong.zhang0 at gmail.com>
Cc: Russell King <rmk+kernel at arm.linux.org.uk>
Cc: Nicolas Pitre <nico at linaro.org>
Cc: Will Deacon <will.deacon at arm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: linux-arm-kernel at lists.infradead.org
Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Yong Zhang 2015-01-29 12:56:18 -06:00 committed by Alibek Omarov
parent 9e1ba85f8d
commit 879e33f32e
1 changed files with 2 additions and 0 deletions
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2
arch/arm/include/asm/cmpxchg.h
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@ -127,6 +127,8 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size
#else /* min ARCH >= ARMv6 */
#define __HAVE_ARCH_CMPXCHG 1
extern void __bad_cmpxchg(volatile void *ptr, int size);
/*