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SubjectRe: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified

On 5/19/2017 8:10 PM, Peter Zijlstra wrote:
> On Fri, May 19, 2017 at 08:06:09PM +0800, Jin, Yao wrote:
>>> I would much rather see this in generic code, somewhere around
>>> __perf_event_overflow() I suppose. That would retain proper accounting
>>> for the interrupt rate etc..
>>> Also it would work for all architectures. Because I'm thinking more than
>>> just x86 will suffer from skid.
>> Yes, moving to generic code is better. Thanks for the suggestion! I will do
>> that.
>>> If you're really worried, I suppose you can put it behind a PERF_PMU_CAP
>>> flag or something.
>> I guess what you are suggesting is to add checking like:
>> if (is_sampling_event(event)) {
>> if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT) {
>> return;
>> }
>> }
> Ah, I was more thinking of something like PERF_PMU_CAP_NO_SKID or
> something that would skip the test and preserve current behaviour.

OK, I understand now. For example, for PEBS event, its capabilities
should be set with PERF_PMU_CAP_NO_SKID.

If the event's capabilities is set with PERF_PMU_CAP_NO_SKID, it should
skip the checking and keep current behavior.

Jin Yao

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