linux-kernel - Re: [PATCH V4 02/16] perf: Only dump the throttle log for the leader

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Message-ID: <20250521120541.GD39944@noisy.programming.kicks-ass.net>
Date: Wed, 21 May 2025 14:05:41 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: kan.liang@...ux.intel.com
Cc: mingo@...hat.com, namhyung@...nel.org, irogers@...gle.com,
	mark.rutland@....com, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org, eranian@...gle.com,
	ctshao@...gle.com, tmricht@...ux.ibm.com, leo.yan@....com
Subject: Re: [PATCH V4 02/16] perf: Only dump the throttle log for the leader

On Tue, May 20, 2025 at 11:16:30AM -0700, kan.liang@...ux.intel.com wrote:
> From: Kan Liang <kan.liang@...ux.intel.com>
> 
> The PERF_RECORD_THROTTLE records are dumped for all throttled events.
> It's not necessary for group events, which are throttled altogether.
> 
> Optimize it by only dump the throttle log for the leader.
> 
> The sample right after the THROTTLE record must be generated by the
> actual target event. It is good enough for the perf tool to locate the
> actual target event.

So while both patches change behaviour; the first patch should preserve
all that was done and simply do more. OTOH this patch explicitly changes
behaviour in that what was done, is now no longer done.

Are we very sure there isn't a tool that expect per event throttle
messages?

I'll take the patches, but I'm somewhat suspect of this one.