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SubjectRe: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
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On Fri, Oct 19, 2012 at 5:49 PM, Andi Kleen <ak@linux.intel.com> wrote:
>> + /*
>> + * for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
>> + * be measured alone on SNB (exclusive PMU access) as per Intel SDM.
>> + */
>> + if ((cfg & INTEL_ARCH_EVENT_MASK) == 0x01c0 && !event->attr.exclusive) {
>> + pr_info("perf: INST_RETIRED.PREC_DIST only works in exclusive mode\n");
>> + return -EINVAL;
>> + }
>
>
> Strictly you have to check for precise too, right?
>
Yes, the restriction is enforced only when PEBS is active and
this is what I do based on where pebs_aliases() is called.


> -Andi


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