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

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Message-ID: <aRz-6jQf9GH4JROi@tassilo>
Date: Tue, 18 Nov 2025 15:19:06 -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

On Tue, Nov 18, 2025 at 01:13:26PM -0800, Ian Rogers wrote:
> Add flag that disables affinity behavior. Using sched_setaffinity to
> place a perf thread on a CPU can avoid certain interprocessor
> interrupts but may introduce a delay due to the scheduling,
> particularly on loaded machines. Add a command line option to disable
> the behavior. This behavior is less present in other tools like `perf
> record`, as it uses a ring buffer and doesn't make repeated system
> calls.

Like i wrote earlier a much better fix for starvation is to use 
real-time priority instead of the old IPI storms this flag 
is bringing back.

-Andi