linux-kernel - Re: [RFC] Adding support for setting the affinity of the recording process

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Message-ID: <20230612150553.GM4253@hirez.programming.kicks-ass.net>
Date:   Mon, 12 Jun 2023 17:05:53 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Yang Jihong <yangjihong1@...wei.com>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] Adding support for setting the affinity of the recording
 process

On Mon, Jun 12, 2023 at 11:24:26AM -0300, Arnaldo Carvalho de Melo wrote:
> But could you please spell out the use case, why do you need this, is
> this so common (for you) that you repeatedly need to first taskset, then
> perf, etc?

I'm thinking this is due to big.LITTLE things where the PMUs on the CPUs
are different. Intel recently having stepped into this trainwreck,
there's now a ton more people 'enjoying' it ...

So what people often do it is affine the process to one type of CPU and
then perf it so that their measurements are consistent.

It all sucks, but given the situation, it might be the best option :/

Ian was working on improving the whole hybrid thing, perhaps he has more
opinions.