Commit 7639dae0 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar

perf, x86: Provide a PEBS capable cycle event

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent abe43400
......@@ -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;
......
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