linux-kernel - Re: [PATCH v5 3/3] perf stat: Add no-affinity flag

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Message-ID: <aR3kN1GiKki4AO9b@tassilo>
Date: Wed, 19 Nov 2025 07:37:27 -0800
From: Andi Kleen <ak@...ux.intel.com>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Dr. David Alan Gilbert" <linux@...blig.org>,
	Yang Li <yang.lee@...ux.alibaba.com>,
	James Clark <james.clark@...aro.org>,
	Thomas Falcon <thomas.falcon@...el.com>,
	Thomas Richter <tmricht@...ux.ibm.com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: Re: [PATCH v5 3/3] perf stat: Add no-affinity flag

> Ack. This is only adding the flag to perf stat, are the storms as much
> of an issue there? Patch 2 of 3 changes it so that for a single event
> we still use affinities, where a dummy and an event count as >1 event.

Not sure I follow here. I thought you disabled it completely?

> We have specific examples of loaded machines where the scheduling
> latency causes broken metrics - the flag at least allows investigation
> of issues like this. I don't mind reviewing a patch adding real time
> priorities as an option.

You don't need a new flag. Just run perf with real time priority with
any standard wrapper tool, like chrt. The main obstacle is that you may
need the capability to do that though.

-Andi