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

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Message-ID: <eba28230-5a96-fbfe-0fb3-191921839a72@linux.intel.com>
Date:   Fri, 19 May 2017 20:06:09 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     acme@...nel.org, jolsa@...nel.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, Linux-kernel@...r.kernel.org,
        ak@...ux.intel.com, kan.liang@...el.com, yao.jin@...el.com,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is
 specified

SNIP

> 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;
     }
}

Is my understanding correct?

Thanks
Jin Yao