Re: [PATCH 2/3] sched/fair: Correctly insert cfs_rq's to list on unthrottle
From: Vincent Guittot <hidden>
Date: 2021-05-28 15:27:20
Also in:
lkml
On Fri, 28 May 2021 at 17:07, Odin Ugedal [off-list ref] wrote:
Hi,quoted
What would be the other condition in addition to the current one :cfs_rq->nr_running >= 1 ?The condition is that if it has load, we should add it (I don't have 100% control on util_avg and runnable_avg tho.). Using "!cfs_rq_is_decayed()" is another way, but imo. that is a bit overkill.
normally tg_load_avg_contrib should be null when cfs_rq_is_decayed()
quoted
We need to add a cfs_rq in the list if it still contributes to the tg->load_avg and the split of the share. Can't we add a condition for this instead of adding a new field ?Yes, using cfs_rq->tg_load_avg_contrib as below would also work the same way. I still think being explicit that we insert it if we have removed it is cleaner in a way, as it makes it consistent with the other use of list_add_leaf_cfs_rq() and list_del_leaf_cfs_rq(), but
The reason of this list is to ensure that the load of all cfs_rq are periodically updated as it is then used to share the runtime between groups so we should keep to use the rule whenever possible.
quoted hunk ↗ jump to hunk
that is about preference I guess. I do however think that using tg_load_avg_contrib will work just fine, as it should always be positive in case the cfs_rq has some load. I can resent v2 of this patch using this instead;diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index ad7556f99b4a..969ae7f930f5 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c@@ -4720,7 +4720,7 @@ static int tg_unthrottle_up(struct task_group*tg, void *data) cfs_rq->throttled_clock_task; /* Add cfs_rq with already running entity in the list */ - if (cfs_rq->nr_running >= 1) + if (cfs_rq->tg_load_avg_contrib)
we probably need to keep (cfs_rq->nr_running >= 1) as we can have case where tg_load_avg_contrib is null but a task is enqueued
list_add_leaf_cfs_rq(cfs_rq);
}