linux-kernel - Re: [PATCH v1 0/3] coresight: Fix for snapshot mode

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Date:   Tue, 22 Jun 2021 20:58:11 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Denis Nikitin <denik@...gle.com>
Cc:     Suzuki K Poulose <Suzuki.Poulose@....com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Leach <mike.leach@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Daniel Kiss <daniel.kiss@....com>,
        Coresight ML <coresight@...ts.linaro.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v1 0/3] coresight: Fix for snapshot mode

Hi Denis,

On Sun, Jun 20, 2021 at 10:21:57PM -1000, Denis Nikitin wrote:

[...]

> > I'd like to leave patch 1/3 out, and resend it if we get conclusion.
> > At the meantime, @Denis, if you have observed any profiling result
> > (or profiling quality) difference caused by patch 1, the feedback would
> > be very valuable.
> 
> I evaluated AutoFDO profiles with benchmarks but I was only focused
> on the system-wide mode. And as I understood patch 1 fixes the issue
> in non system-wide mode.

Yes, patch 1 doesn't work for the system-wide mode.  In the system-wide
mode, CoreSight driver has its own reference counter to only allow the
last CPU to fill trace data to AUX buffer.

> Currently I'm OoO so I won't be able to do further evaluation.

No problem, thanks for the feedback!

Leo