Re: min_vruntime update when a task is sleeping/migrating
From: Peter Zijlstra
Date: Thu Feb 23 2017 - 04:51:06 EST
On Thu, Feb 23, 2017 at 11:45:26AM +0530, Pavan Kondeti wrote:
> 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?
Hurm, yes that comment and the code are not in agreement :/
Having gone over the code again, I think the comment is right and the
code is wrong, but it would be good to double check that.
> static void
> dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> * 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)