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

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Message-ID: <4e2ad815-a8f8-4800-b389-6b8a79bcf04e@arm.com>
Date: Wed, 11 Sep 2024 13:49:59 +0200
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Peter Zijlstra <peterz@...radead.org>, Mike Galbraith <efault@....de>
Cc: Luis Machado <luis.machado@....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
Subject: Re: [PATCH 10/24] sched/uclamg: Handle delayed dequeue

On 11/09/2024 11:13, Peter Zijlstra wrote:
> On Wed, Sep 11, 2024 at 11:10:26AM +0200, Mike Galbraith wrote:
>> On Wed, 2024-09-11 at 10:45 +0200, Peter Zijlstra wrote:
>>> On Wed, Sep 11, 2024 at 09:35:16AM +0100, Luis Machado wrote:

[...]

>>>> So probably an unexpected decrement or lack of an increment somewhere.
>>>
>>> Yeah, that's buggered. Ok, I'll go rebase sched/core and take this patch
>>> out. I'll see if I can reproduce that.
>>
>> Hm, would be interesting to know how the heck he's triggering that.
>>
>> My x86_64 box refuses to produce any such artifacts with anything I've
>> tossed at it, including full LTP with enterprise RT and !RT configs,
>> both in master and my local SLE15-SP7 branch.  Hohum.
> 
> Yeah, my hackbench runs also didn't show that. Perhaps something funny
> with cgroups. I didn't test cgroup bandwidth for exanple.

Don't see it either on my Arm64 Juno-r0 (6 CPUs) with:

cgexec -g cpu:/A/B/C hackbench -l 1000

We are checking the Pixel6 now.