linux-kernel - min_vruntime update when a task is sleeping/migrating

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Date:   Thu, 23 Feb 2017 11:45:26 +0530
From:   Pavan Kondeti <pkondeti@...eaurora.org>
To:     linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>
Subject: min_vruntime update when a task is sleeping/migrating

Hi Peter,

The comment and the code around 2nd update_min_vruntime() call in
dequeue_entity() are not matching. If I understand commit b60205c7c558
("sched/fair: Fix min_vruntime tracking") correctly, the check is
inverted there. We want to update min_vruntime when a task is
sleeping/migrating. is my understanding right?

static void
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{

 <snip>
  /*
   * Now advance min_vruntime if @se was the entity holding it back,
   * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
   * put back on, and if we advance min_vruntime, we'll be placed back
   * further than we started -- ie. we'll be penalized.
   */
   if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
      update_min_vruntime(cfs_rq);
}

Thanks,
Pavan

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