linux-kernel - Re: [PATCH V6 3/3] perf/x86/intel: Support PEBS counters snapshotting

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Message-ID: <20241218163249.GI2354@noisy.programming.kicks-ass.net>
Date: Wed, 18 Dec 2024 17:32:49 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: kan.liang@...ux.intel.com
Cc: mingo@...hat.com, acme@...nel.org, namhyung@...nel.org,
	irogers@...gle.com, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org, ak@...ux.intel.com,
	eranian@...gle.com, dapeng1.mi@...ux.intel.com
Subject: Re: [PATCH V6 3/3] perf/x86/intel: Support PEBS counters snapshotting

On Wed, Dec 18, 2024 at 07:16:43AM -0800, kan.liang@...ux.intel.com wrote:

> To prevent the case that a PEBS record value might be in the past
> relative to what is already in the event, perf always stops the PMU and
> drains the PEBS buffer before updating the corresponding event->count.

Like I wrote here:

  https://lkml.kernel.org/r/20241218082404.GI11133@noisy.programming.kicks-ass.net

I don't think this is sufficient.