Messages in this thread | | | From | Paul Turner <> | Date | Mon, 16 May 2011 05:56:56 -0700 | Subject | Re: [patch 05/15] sched: add a timer to handle CFS bandwidth refresh |
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On Mon, May 16, 2011 at 3:18 AM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > On Tue, 2011-05-03 at 02:28 -0700, Paul Turner wrote: >> @@ -1003,6 +1003,8 @@ enqueue_entity(struct cfs_rq *cfs_rq, st >> >> if (cfs_rq->nr_running == 1) >> list_add_leaf_cfs_rq(cfs_rq); >> + >> + start_cfs_bandwidth(cfs_rq); >> } >> >> static void __clear_buddies_last(struct sched_entity *se) >> @@ -1220,6 +1222,8 @@ static void put_prev_entity(struct cfs_r >> update_stats_wait_start(cfs_rq, prev); >> /* Put 'current' back into the tree. */ >> __enqueue_entity(cfs_rq, prev); >> + >> + start_cfs_bandwidth(cfs_rq); >> } >> cfs_rq->curr = NULL; >> } > > OK, so while the first made sense the second had me go wtf?!, now I > _think_ you do that because do_sched_cfs_period_timer() can return idle > and stop the timer when no bandwidth consumption is seen for a while, > and thus we need to re-start the timer when we put the entity to sleep, > since that could have been a throttle. > > If that's so then neither really do make sense and a big fat comment is > missing. > > So why not start on the same (but inverse) condition that makes it stop? >
This was originally to guard the case that an entity was running on stale (from a previous period) quota resulting in cfs_bandwidth->idle and the timer not being re-instantiated.
Now that expiration is properly integrated I think the two cases are analogous and that this can be dropped (and the start moved into the (nr_running == 1) entity case on enqueue).
I think this is correct but my brain's a little fuzzy right now, will confirm in the morning. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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