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

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Date:   Mon, 11 Dec 2017 07:34:49 -0800
From:   Tejun Heo <tj@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [RFC] Sharing PMU counters across compatible events

Hello, Jiri.

On Wed, Dec 06, 2017 at 12:42:04PM +0100, Jiri Olsa wrote:
> I see this rather on the hw level, since it concerns HW counters
> 
> I think we could detect same (alias) events at the time counters
> are added/removed on/from the cpu and share their HW part like
> counter idx, regs and such (struct hw_perf_event_cpu in my changes)
> 
> this way it'd be completely transparent for generic code

I don't quite follow why doing this in arch code is better than
generic.  Doing this in arch means we'd need to do the same thing
multiple times for different archs.  Why is that better?

Thanks.

-- 
tejun