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

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Message-ID: <b269e539-3256-4ff0-b2ab-0cd558ac841f@linux.intel.com>
Date: Mon, 8 Dec 2025 13:16:54 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Ian Rogers <irogers@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
 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 12/6/2025 7:44 AM, Ian Rogers wrote:
> 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.

Base on the logic, it looks we need to add the flag EF_UPDATE in
perf_event_throttle_group(), but need Peter's confirm. 


>
> Thanks,
> Ian
>