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Subject: Re: [RFC] Adding support for setting the affinity of the recording
 process
To:     Peter Zijlstra <peterz@infradead.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>
CC:     Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        linux-perf-users <linux-perf-users@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
References: <159de73b-fdd6-6df8-4f77-73c628fe641f@huawei.com>
 <ZIcqmlHIfBbyZFDl@kernel.org>
 <20230612150553.GM4253@hirez.programming.kicks-ass.net>
From:   Yang Jihong <yangjihong1@huawei.com>
Message-ID: <47f5ddbd-f1cb-1da7-cfca-af67962e6797@huawei.com>
Date:   Tue, 13 Jun 2023 10:11:06 +0800
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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.