linux-kernel - Re: [PATCH 0/10 v2] sched/fair: Fix statistics with delayed dequeue

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Message-ID: <dacfbe5d-a730-4643-90a8-1c38cb6780da@arm.com>
Date: Mon, 2 Dec 2024 09:23:35 +0000
From: Luis Machado <luis.machado@....com>
To: Vincent Guittot <vincent.guittot@...aro.org>,
 Mike Galbraith <efault@....de>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
 dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
 mgorman@...e.de, vschneid@...hat.com, linux-kernel@...r.kernel.org,
 kprateek.nayak@....com, pauld@...hat.com
Subject: Re: [PATCH 0/10 v2] sched/fair: Fix statistics with delayed dequeue

On 12/2/24 09:17, Vincent Guittot wrote:
> On Sun, 1 Dec 2024 at 14:30, Mike Galbraith <efault@....de> wrote:
>>
>> Greetings,
>>
>> On Fri, 2024-11-29 at 17:17 +0100, Vincent Guittot wrote:
>>> Delayed dequeued feature keeps a sleeping sched_entitiy enqueued until its
>>> lag has elapsed. As a result, it stays also visible in the statistics that
>>> are used to balance the system and in particular the field h_nr_running.
>>>
>>> This serie fixes those metrics by creating a new h_nr_queued that tracks
>>> all queued tasks. It renames h_nr_running into h_nr_runnable and restores
>>> the behavior of h_nr_running i.e. tracking the number of fair tasks that
>>>  want to run.
>>>
>>> h_nr_runnable is used in several places to make decision on load balance:
>>>   - PELT runnable_avg
>>>   - deciding if a group is overloaded or has spare capacity
>>>   - numa stats
>>>   - reduced capacity management
>>>   - load balance between groups
>>
>> I took the series for a spin in tip v6.12-10334-gb1b238fba309, but
>> runnable seems to have an off-by-one issue, causing it to wander ever
>> further south.
>>
>> patches 1-3 applied.
>>   .h_nr_runnable                 : -3046
>>   .runnable_avg                  : 450189777126
> 
> Yeah, I messed up something around finish_delayed_dequeue_entity().
> I'm' going to prepare a v3> 

Maybe something similar to what I ran into here?

https://lore.kernel.org/lkml/6df12fde-1e0d-445f-8f8a-736d11f9ee41@arm.com/

>>
>> full set applied.
>>   .h_nr_runnable                 : -5707
>>   .runnable_avg                  : 4391793519526
>>
>>         -Mike