linux-kernel - Re: [PATCH v6 0/2] sched: Optionally skip uclamp logic in fast path

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Message-ID: <20200706104111.yfopcjm3kiqlxhx2@e107158-lin.cambridge.arm.com>
Date:   Mon, 6 Jul 2020 11:41:12 +0100
From:   Qais Yousef <qais.yousef@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Patrick Bellasi <patrick.bellasi@...bug.net>,
        Chris Redpath <chris.redpath@....com>,
        Lukasz Luba <lukasz.luba@....com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 0/2] sched: Optionally skip uclamp logic in fast path

On 07/03/20 14:09, Vincent Guittot wrote:
> I have run the perf bench sched pipe that have have already run
> previously with this v6 and the results are similar to my previous
> tests:
> The impact is -1.61% similarly to v2 which is better compared the
> original -3.66% without your patch

Thanks Vincent.

Can you afford doing a capture of `perf record` and share the resulting
perf.dat with vmlinux (with debug symbols)?

Having a before/after capture would be even better.

Not sure if we can do  much about this -1.61% in your case, but it'd be good to
understand why if possible. perf bench sched pipe is very sensitive to tiniest
of changes which could be due to binary-to-binary differences.

Thanks

--
Qais Yousef