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perf, x86: Provide a PEBS capable cycle event

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Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2010-12-14 21:26:40 +01:00 committed by Ingo Molnar
parent abe4340057
commit 7639dae0ca
1 changed files with 26 additions and 0 deletions
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26
arch/x86/kernel/cpu/perf_event_intel.c
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@ -816,6 +816,32 @@ static int intel_pmu_hw_config(struct perf_event *event)
if (ret)
return ret;
if (event->attr.precise_ip &&
(event->hw.config & X86_RAW_EVENT_MASK) == 0x003c) {
/*
* Use an alternative encoding for CPU_CLK_UNHALTED.THREAD_P
* (0x003c) so that we can use it with PEBS.
*
* The regular CPU_CLK_UNHALTED.THREAD_P event (0x003c) isn't
* PEBS capable. However we can use INST_RETIRED.ANY_P
* (0x00c0), which is a PEBS capable event, to get the same
* count.
*
* INST_RETIRED.ANY_P counts the number of cycles that retires
* CNTMASK instructions. By setting CNTMASK to a value (16)
* larger than the maximum number of instructions that can be
* retired per cycle (4) and then inverting the condition, we
* count all cycles that retire 16 or less instructions, which
* is every cycle.
*
* Thereby we gain a PEBS capable cycle counter.
*/
u64 alt_config = 0x108000c0; /* INST_RETIRED.TOTAL_CYCLES */
alt_config |= (event->hw.config & ~X86_RAW_EVENT_MASK);
event->hw.config = alt_config;
}
if (event->attr.type != PERF_TYPE_RAW)
return 0;