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Message-ID: <deef7d82-eae8-6f37-6c6d-fcb3523df97d@arm.com>
Date: Fri, 21 Oct 2016 13:19:01 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Vincent Guittot <vincent.guittot@...aro.org>, peterz@...radead.org,
mingo@...nel.org, linux-kernel@...r.kernel.org
Cc: yuyang.du@...el.com, Morten.Rasmussen@....com,
linaro-kernel@...ts.linaro.org, pjt@...gle.com, bsegall@...gle.com,
kernellwp@...il.com
Subject: Re: [PATCH 4/6 v5] sched: propagate load during synchronous
attach/detach
On 10/17/2016 10:14 AM, Vincent Guittot wrote:
> When a task moves from/to a cfs_rq, we set a flag which is then used to
> propagate the change at parent level (sched_entity and cfs_rq) during
> next update. If the cfs_rq is throttled, the flag will stay pending until
> the cfs_rw is unthrottled.
minor nit:
s/cfs_rw/cfs_rq
[...]
> @@ -8704,6 +8867,22 @@ static void detach_task_cfs_rq(struct task_struct *p)
> update_load_avg(se, 0);
> detach_entity_load_avg(cfs_rq, se);
> update_tg_load_avg(cfs_rq, false);
> +
> +#ifdef CONFIG_FAIR_GROUP_SCHED
> + /*
> + * Propagate the detach across the tg tree to make it visible to the
> + * root
> + */
> + se = se->parent;
> + for_each_sched_entity(se) {
> + cfs_rq = cfs_rq_of(se);
> +
> + if (cfs_rq_throttled(cfs_rq))
> + break;
> +
> + update_load_avg(se, UPDATE_TG);
> + }
> +#endif
> }
>
> static void attach_entity_cfs_rq(struct sched_entity *se)
> @@ -8722,6 +8901,22 @@ static void attach_entity_cfs_rq(struct sched_entity *se)
> update_load_avg(se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
> attach_entity_load_avg(cfs_rq, se);
> update_tg_load_avg(cfs_rq, false);
> +
> +#ifdef CONFIG_FAIR_GROUP_SCHED
> + /*
> + * Propagate the attach across the tg tree to make it visible to the
> + * root
> + */
> + se = se->parent;
> + for_each_sched_entity(se) {
> + cfs_rq = cfs_rq_of(se);
> +
> + if (cfs_rq_throttled(cfs_rq))
> + break;
> +
> + update_load_avg(se, UPDATE_TG);
> + }
> +#endif
> }
The 'detach across' and 'attach across' in detach_task_cfs_rq() and
attach_entity_cfs_rq() do the same so couldn't you not create a function
propagate_foo() for it? This would avoid this ifdef as well.
You could further create in your '[PATCH 1/6 v5] sched: factorize attach
entity':
detach_entity_cfs_rq() {
update_load_avg()
detach_entity_load_avg()
update_tg_load_avg()
propagate_load_avg()
}
and then we would have:
attach_task_cfs_rq() -> attach_entity_cfs_rq() -> propagate_foo()
detach_task_cfs_rq() -> detach_entity_cfs_rq() -> propagate_foo()
I guess you didn't because it would be only called one time but this
symmetric approaches are easier to remember (at least for me).
[...]
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