linux-kernel - Re: [PATCH 10/24] sched/uclamg: Handle delayed dequeue

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Message-ID: <20240910140524.GH4723@noisy.programming.kicks-ass.net>
Date: Tue, 10 Sep 2024 16:05:24 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Luis Machado <luis.machado@....com>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Hongyan Xia <hongyan.xia2@....com>, mingo@...hat.com,
	juri.lelli@...hat.com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, vschneid@...hat.com, linux-kernel@...r.kernel.org,
	kprateek.nayak@....com, wuyun.abel@...edance.com,
	youssefesmat@...omium.org, tglx@...utronix.de, efault@....de
Subject: Re: [PATCH 10/24] sched/uclamg: Handle delayed dequeue

On Tue, Sep 10, 2024 at 12:04:11PM +0100, Luis Machado wrote:
> I gave the above patch a try on our Android workload running on the Pixel 6 with a 6.8-based kernel.
> 
> First I'd like to confirm that Dietmar's fix that was pushed to tip:sched/core (Fix util_est
> accounting for DELAY_DEQUEUE) helps bring the frequencies and power use down to more sensible levels.
> 
> As for the above changes, unfortunately I'm seeing high frequencies and high power usage again. The
> pattern looks similar to what we observed with the uclamp inc/dec imbalance.

:-(

> I haven't investigated this in depth yet, but I'll go stare at some traces and the code, and hopefully
> something will ring bells.

So first thing to do is trace h_nr_delayed I suppose, in my own
(limited) testing that was mostly [0,1] correctly correlating to there
being a delayed task on the runqueue.

I'm assuming that removing the usage sites restores function?