linux-kernel - Re: [PATCH v1 3/3] perf parse-events: Add 'X' modifier to exclude an event from being regrouped

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Message-ID: <CAP-5=fUvppttK3t7GHsWyan08bZJRkv4-M_P2vJpe50bOuiCYA@mail.gmail.com>
Date: Fri, 17 Oct 2025 09:59:20 -0700
From: Ian Rogers <irogers@...gle.com>
To: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	James Clark <james.clark@...aro.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Yoshihiro Furudera <fj5100bi@...itsu.com>, Howard Chu <howardchu95@...il.com>, 
	Thomas Falcon <thomas.falcon@...el.com>, Andi Kleen <ak@...ux.intel.com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Xudong Hao <xudong.hao@...el.com>
Subject: Re: [PATCH v1 3/3] perf parse-events: Add 'X' modifier to exclude an
 event from being regrouped

On Fri, Oct 17, 2025 at 12:25 AM Mi, Dapeng <dapeng1.mi@...ux.intel.com> wrote:
> Hi Ian,
>
> It looks the "X" modifier only works for the cases without explicit group,
> like this.
>
> sudo ./perf record -e cpu/mem-stores/ppu,cpu/slots/uX -- sleep 1
> [ perf record: Woken up 2 times to write data ]
> [ perf record: Captured and wrote 0.019 MB perf.data (7 samples) ]
>
> Once there is an explicit group, the "X" modifier would not work and the
> regroup still happens, e.g.,
>
> sudo ./perf record -e '{cpu/mem-stores/ppu,cpu/slots/uX}' -- sleep 1
> WARNING: events were regrouped to match PMUs
> [ perf record: Woken up 2 times to write data ]
> [ perf record: Captured and wrote 0.019 MB perf.data (7 samples) ]
>
> I suppose we should enhance the "X" modifier and make it work in 2nd case
> as well. How's your idea?

Hi Dapeng,

hopefully fixed in:
https://lore.kernel.org/lkml/20251017165753.206608-1-irogers@google.com/

PTAL. Thanks,
Ian




> Thanks,
>
> Dapeng Mi
>
> > ference|ops|access|misses|miss)