linux-kernel - Re: [PATCH v2] freezer,sched: Use saved_state to reduce some spurious wakeups

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Message-ID: <20230908220804.GA29218@noisy.programming.kicks-ass.net>
Date:   Sat, 9 Sep 2023 00:08:04 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Elliot Berman <quic_eberman@...cinc.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>,
        Thomas Gleixner <tglx@...utronix.de>, kernel@...cinc.com,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org,
        Prakash Viswalingam <quic_prakashv@...cinc.com>
Subject: Re: [PATCH v2] freezer,sched: Use saved_state to reduce some
 spurious wakeups

On Fri, Sep 08, 2023 at 01:08:07PM -0700, Elliot Berman wrote:

> > Perhaps we should start off by doing the below, instead of making it
> > more complicated instead. I suppose you're right about the overhead, but
> > run a hackbench just to make sure or something.
> > 
> 
> I ran perf bench sched message -g 40 -l 40 with the v3 patch [1]. After 60
> iterations each, I don't see a significant difference on my arm64 platform:
> both samples ~normal and ~eq variance w/t-test p-value: 0.79.
> 
> We also ran typical high level benchmarks for our SoCs (antutu,
> geekbench, et. al) and didn't see any regressions there.

So if you would've made this 2 patches, the first removing the ifdef,
then the changelog for that patch would be a good place to mention it
doesn't measurably regress things.

As a bonus, it then makes your other changes smaller too ;-)