linux-kernel - Re: [RFC] Sharing PMU counters across compatible events

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Message-ID: <20171213161829.GV3919388@devbig577.frc2.facebook.com>
Date:   Wed, 13 Dec 2017 08:18:29 -0800
From:   Tejun Heo <tj@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org, kernel-team@...com,
        alexey.budankov@...ux.intel.com
Subject: Re: [RFC] Sharing PMU counters across compatible events

Hello, Peter.

On Tue, Dec 12, 2017 at 11:37:36PM +0100, Peter Zijlstra wrote:
> That would be a fairly massive change from how perf works today. And the
> obvious pain point would be changing the per-cpu event set, which would
> mean recomputing all possible combinations of task sets.
> 
> Also note that each context (cpu,task) is allowed to have more events
> than fit on the PMU, at which point we'll start rotating events. Do we
> also pre-compute all possible rotation sets?
> 
> Just not quite seeing this..

Yeah, right.  Will think more about it

Thanks.

-- 
tejun