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perf, x86: Use ALTERNATIVE() to check for X86_FEATURE_PERFCTR_CORE

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Using ALTERNATIVE() when checking for X86_FEATURE_PERFCTR_CORE avoids
an extra pointer chase and data cache hit.

Signed-off-by: Robert Richter <robert.richter@amd.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1302913676-14352-4-git-send-email-robert.richter@amd.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Robert Richter 2011-04-16 02:27:55 +02:00 committed by Ingo Molnar
parent 68d2cf25d3
commit c8e5910edf
1 changed files with 11 additions and 4 deletions
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15
arch/x86/kernel/cpu/perf_event.c
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@ -31,6 +31,7 @@
#include <asm/nmi.h> #include <asm/nmi.h>
#include <asm/compat.h> #include <asm/compat.h>
#include <asm/smp.h> #include <asm/smp.h>
#include <asm/alternative.h>
#if 0 #if 0
#undef wrmsrl #undef wrmsrl
@ -363,12 +364,18 @@ again:
return new_raw_count; return new_raw_count;
} }
/* using X86_FEATURE_PERFCTR_CORE to later implement ALTERNATIVE() here */
static inline int x86_pmu_addr_offset(int index) static inline int x86_pmu_addr_offset(int index)
{ {
if (boot_cpu_has(X86_FEATURE_PERFCTR_CORE)) int offset;
return index << 1;
return index; /* offset = X86_FEATURE_PERFCTR_CORE ? index << 1 : index */
alternative_io(ASM_NOP2,
"shll $1, %%eax",
X86_FEATURE_PERFCTR_CORE,
"=a" (offset),
"a" (index));
return offset;
} }
static inline unsigned int x86_pmu_config_addr(int index) static inline unsigned int x86_pmu_config_addr(int index)