linux-kernel - Re: [RFC PATCH] sched/util_est: Do not sub the delayed-task's util-est

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Message-ID: <e4f331d6-1724-4f6d-8dbb-bd07fe82229f@arm.com>
Date: Mon, 24 Mar 2025 14:22:44 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Xuewen Yan <xuewen.yan94@...il.com>
Cc: Xuewen Yan <xuewen.yan@...soc.com>, vincent.guittot@...aro.org,
 mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
 rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
 vschneid@...hat.co, linux-kernel@...r.kernel.org, hongyan.xia2@....com,
 qyousef@...alina.io, ke.wang@...soc.com, di.shen@...soc.com
Subject: Re: [RFC PATCH] sched/util_est: Do not sub the delayed-task's
 util-est

On 21/03/2025 07:44, Xuewen Yan wrote:
> Hi hongyan
> 
> On Wed, Mar 19, 2025 at 9:33 PM Dietmar Eggemann
> <dietmar.eggemann@....com> wrote:
>>
>> On 14/03/2025 10:09, Xuewen Yan wrote:
>>> In cpu_util_without, When the task is in rq, we should
>>> sub the task's util_est, however, the delayed_task->on_rq
>>> is true, however, the delayed_task's util had been sub
>>> when sleep, so there is no need to sub the delayed task's
>>> util-est. So add the checking of delayed-task.
>>>
>>> On the other hand, as said in [1], the logic of util_est's
>>> enqueue/dequeue could be simplified.
>>> So simplify it by aligning with the conditions of uclamp.
>>
>> This flag simplification looks good to me.
>>
>> IMHO, you should submit this with the uclamp change so that we can call
>> uclamp_rq_inc() before p->sched_class->enqueue_task(). To make sure the
>> task which is enqueued with 'flags & ENQUEUE_DELAYED' is considered for
>> cpufreq_update_util() in enqueue_task_fair() (Hongyan's finding in
>> https://lkml.kernel.org/r/84441660bef0a5e67fd09dc3787178d0276dad31.1740664400.git.hongyan.xia2@arm.com)
>>
>> I would prefer the less invasive fix you presented here:
>>
>> https://lkml.kernel.org/r/CAB8ipk9LpbiUDnbcV6+59+Sa=Ai7tFzO===mpLD3obNdV4=J-A@mail.gmail.com
>>
>> since uclamp is already a core thing (fair + rt), it works for current
>> max aggregation and it's less invasive.
>>
> 
> Since the uclamp's enqueue is affecting performance, could we fix the
> uclamp-enqueue issue first?
> Need I to send the patch-v2 base the
> https://lore.kernel.org/all/CAB8ipk9LpbiUDnbcV6+59+Sa=Ai7tFzO===mpLD3obNdV4=J-A@mail.gmail.com/T/#mb32d7675beda5cadc35a3c04cddebc39580c718b
> ?

That would be nice. Maybe a patch-set with 1) uclamp enqueue fix and 2)
util_est flag simplification? So those two things stay together ...

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