linux-kernel - Re: [PATCH] perf: Fix 0 count issue of cpu-clock

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Message-ID: <CAP-5=fWg9gNW5OZV=JD7dcpf-FBtKXLCR_0Caz8a=SxbvNQ-HQ@mail.gmail.com>
Date: Fri, 5 Dec 2025 15:44:52 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>, 
	Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Andi Kleen <ak@...ux.intel.com>, 
	Eranian Stephane <eranian@...gle.com>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, Dapeng Mi <dapeng1.mi@...el.com>, 
	Zide Chen <zide.chen@...el.com>, Falcon Thomas <thomas.falcon@...el.com>, 
	Xudong Hao <xudong.hao@...el.com>
Subject: Re: [PATCH] perf: Fix 0 count issue of cpu-clock

On Tue, Nov 18, 2025 at 3:24 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Tue, Nov 18, 2025 at 07:22:24PM +0800, Mi, Dapeng wrote:
> >
> > On 11/18/2025 7:04 PM, Peter Zijlstra wrote:
> > > On Tue, Nov 18, 2025 at 12:03:09PM +0100, Peter Zijlstra wrote:
> > >> Also, the few comments we do have already note that ->del() must do
> > >> ->stop(EF_UPDATE).

Hi Peter,

I was trying to do a quick sanity check that other callers of stop
were passing in EF_UPDATE. I wondered if the case of
perf_event_throttle_group with leader sampling has an issue? The
throttle should only happen on an event or group leader that is in
sampling mode, but the group members could be non-sampling with leader
sampling. Sorry for the noise if I'm wrong on this. Fwiw, the other
uses either pass in EF_UPDATE or I think for  __perf_event_aux_pause
and  __perf_event_overflow the problem isn't relevant.

Thanks,
Ian