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Message-ID: <CAKfTPtDFzRMwSkOr25y5+HibWLgjpc34V3G82KrFPbMjU+ts5w@mail.gmail.com>
Date: Mon, 29 May 2017 15:41:20 +0200
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Tejun Heo <tj@...nel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Mike Galbraith <efault@....de>, Paul Turner <pjt@...gle.com>,
Chris Mason <clm@...com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Morten Rasmussen <morten.rasmussen@....com>,
Ben Segall <bsegall@...gle.com>,
Yuyang Du <yuyang.du@...el.com>
Subject: Re: [RFC][PATCH 06/14] sched/fair: Move enqueue migrate handling
On 12 May 2017 at 18:44, Peter Zijlstra <peterz@...radead.org> wrote:
> Move the entity migrate handling from enqueue_entity_load_avg() to
> update_load_avg(). This has two benefits:
>
> - {en,de}queue_entity_load_avg() will become purely about managing
> runnable_load
>
> - we can avoid a double update_tg_load_avg() and reduce pressure on
> the global tg->shares cacheline
>
> The reason we do this is so that we can change update_cfs_shares() to
> change both weight and (future) runnable_weight. For this to work we
> need to have the cfs_rq averages up-to-date (which means having done
> the attach), but we need the cfs_rq->avg.runnable_avg to not yet
> include the se's contribution (since se->on_rq == 0).
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---
> kernel/sched/fair.c | 70 ++++++++++++++++++++++++++--------------------------
> 1 file changed, 36 insertions(+), 34 deletions(-)
>
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3418,34 +3418,6 @@ update_cfs_rq_load_avg(u64 now, struct c
> return decayed || removed_load;
> }
>
> -/*
> - * Optional action to be done while updating the load average
> - */
> -#define UPDATE_TG 0x1
> -#define SKIP_AGE_LOAD 0x2
> -
> -/* Update task and its cfs_rq load average */
> -static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> -{
> - u64 now = cfs_rq_clock_task(cfs_rq);
> - struct rq *rq = rq_of(cfs_rq);
> - int cpu = cpu_of(rq);
> - int decayed;
> -
> - /*
> - * Track task load average for carrying it to new CPU after migrated, and
> - * track group sched_entity load average for task_h_load calc in migration
> - */
> - if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
> - __update_load_avg_se(now, cpu, cfs_rq, se);
> -
> - decayed = update_cfs_rq_load_avg(now, cfs_rq, true);
> - decayed |= propagate_entity_load_avg(se);
> -
> - if (decayed && (flags & UPDATE_TG))
> - update_tg_load_avg(cfs_rq, 0);
> -}
> -
> /**
> * attach_entity_load_avg - attach this entity to its cfs_rq load avg
> * @cfs_rq: cfs_rq to attach to
> @@ -3486,17 +3458,46 @@ static void detach_entity_load_avg(struc
> cfs_rq_util_change(cfs_rq);
> }
>
> +/*
> + * Optional action to be done while updating the load average
> + */
> +#define UPDATE_TG 0x1
> +#define SKIP_AGE_LOAD 0x2
> +#define DO_ATTACH 0x4
> +
> +/* Update task and its cfs_rq load average */
> +static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> +{
> + u64 now = cfs_rq_clock_task(cfs_rq);
> + struct rq *rq = rq_of(cfs_rq);
> + int cpu = cpu_of(rq);
> + int decayed;
> +
> + /*
> + * Track task load average for carrying it to new CPU after migrated, and
> + * track group sched_entity load average for task_h_load calc in migration
> + */
> + if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
> + __update_load_avg_se(now, cpu, cfs_rq, se);
> +
> + decayed = update_cfs_rq_load_avg(now, cfs_rq, true);
> + decayed |= propagate_entity_load_avg(se);
> +
> + if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
> +
> + attach_entity_load_avg(cfs_rq, se);
> + update_tg_load_avg(cfs_rq, 0);
> +
> + } else if (decayed && (flags & UPDATE_TG))
> + update_tg_load_avg(cfs_rq, 0);
> +}
> +
> /* Add the load generated by se into cfs_rq's load average */
> static inline void
> enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
> {
> cfs_rq->runnable_load_avg += se->avg.load_avg;
> cfs_rq->runnable_load_sum += se_weight(se) * se->avg.load_sum;
> -
> - if (!se->avg.last_update_time) {
> - attach_entity_load_avg(cfs_rq, se);
> - update_tg_load_avg(cfs_rq, 0);
> - }
> }
>
> /* Remove the runnable load generated by se from cfs_rq's runnable load average */
> @@ -3586,6 +3587,7 @@ update_cfs_rq_load_avg(u64 now, struct c
>
> #define UPDATE_TG 0x0
> #define SKIP_AGE_LOAD 0x0
> +#define DO_ATTACH 0x0
>
> static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
> {
> @@ -3740,7 +3742,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, st
> * its group cfs_rq
> * - Add its new weight to cfs_rq->load.weight
> */
> - update_load_avg(cfs_rq, se, UPDATE_TG);
> + update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
> enqueue_entity_load_avg(cfs_rq, se);
> update_cfs_shares(se);
> account_entity_enqueue(cfs_rq, se);
>
>
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