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

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Date:   Tue, 13 Jun 2023 10:11:06 +0800
From:   Yang Jihong <yangjihong1@...wei.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
CC:     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

Hello,

On 2023/6/12 23:05, Peter Zijlstra wrote:
> 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.
Yes, it's a scene, the purpose of setting affinity is to ensure the 
stability of recorded events.

> 
> 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.
>
Thank you for your reply.

> .
> 

Thanks,
Yang.