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Date:   Wed, 11 Jul 2018 10:43:28 +0200
From:   Dietmar Eggemann <>
To:     Joel Fernandes <>
Cc:     Peter Zijlstra <>,
        Ingo Molnar <>,
        Vincent Guittot <>,
        Morten Rasmussen <>,
        Patrick Bellasi <>,
        Quentin Perret <>,, Joel Fernandes <>,
Subject: Re: [PATCH] sched/fair: Remove setting task's se->runnable_weight
 during PELT update

On 07/11/2018 01:09 AM, Joel Fernandes wrote:
> On Mon, Jul 09, 2018 at 05:47:53PM +0100, Dietmar Eggemann wrote:
>> se->runnable_weight must always be in sync with its se->load.weight.
>> se->runnable_weight is set to se->load.weight when the task is
>> forked (init_entity_runnable_average()) or reniced (reweight_entity()).
>> There are two cases in set_load_weight() which since they currently only
>> set se->load.weight could lead to a situation in which se->load.weight
>> is different to se->runnable_weight for a CFS task:
>> (1) A task switches to SCHED_IDLE.
>> (2) A SCHED_FIFO, SCHED_RR or SCHED_DEADLINE task which has been reniced
>>      (during which only its static priority gets set) switches to
>> Set se->runnable_weight to se->load.weight in these two cases to prevent
>> this. This eliminates the need to explicitly set it to se->load.weight
>> during PELT updates in the CFS scheduler fastpath.
> Looks good to me. By the way just asking, is there a chance where
> se_weight(se) and se_runnable(se) can ever be different?

Yes they can be different, not for a task though but for se's 
representing task groups. It got introduced to be able to propagate load 
and runnable load independently through the task groups hierarchies.

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