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Message-ID: <CAKfTPtAw1f89d4Sv+vSfytP8pJy-fy1hvpcz-=hoz4nrZXQV6A@mail.gmail.com>
Date: Tue, 3 Sep 2019 17:38:43 +0200
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Rik van Riel <riel@...riel.com>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
Kernel Team <kernel-team@...com>, Paul Turner <pjt@...gle.com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Morten Rasmussen <morten.rasmussen@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Mel Gorman <mgorman@...hsingularity.net>
Subject: Re: [PATCH 09/15] sched,fair: refactor enqueue/dequeue_entity
Hi Rik,
On Thu, 22 Aug 2019 at 04:18, Rik van Riel <riel@...riel.com> wrote:
>
> Refactor enqueue_entity, dequeue_entity, and update_load_avg, in order
> to split out the things we still want to happen at every level in the
> cgroup hierarchy with a flat runqueue from the things we only need to
> happen once.
>
> No functional changes.
>
> Signed-off-by: Rik van Riel <riel@...riel.com>
> ---
> kernel/sched/fair.c | 64 +++++++++++++++++++++++++++++----------------
> 1 file changed, 42 insertions(+), 22 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 74ee22c59d13..7b0d95f2e3a8 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3502,7 +3502,7 @@ static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
> #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)
> +static inline bool update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> {
> u64 now = cfs_rq_clock_pelt(cfs_rq);
> int decayed;
> @@ -3531,6 +3531,8 @@ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
>
> } else if (decayed && (flags & UPDATE_TG))
> update_tg_load_avg(cfs_rq, 0);
> +
> + return decayed;
This is a functional change, isn't it ?
update_cfs_group is now called only if decayed but we can we attach a
task during the enqueue and there is no decay
>
> }
>
> #ifndef CONFIG_64BIT
> @@ -3747,9 +3749,10 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
> #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)
> +static inline bool update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
> {
> cfs_rq_util_change(cfs_rq, 0);
> + return false;
> }
>
> static inline void remove_entity_load_avg(struct sched_entity *se) {}
> @@ -3872,6 +3875,24 @@ static inline void check_schedstat_required(void)
> * CPU and an up-to-date min_vruntime on the destination CPU.
> */
>
> +static bool
> +enqueue_entity_groups(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> +{
> + /*
> + * When enqueuing a sched_entity, we must:
> + * - Update loads to have both entity and cfs_rq synced with now.
> + * - Add its load to cfs_rq->runnable_avg
> + * - For group_entity, update its weight to reflect the new share of
> + * its group cfs_rq
> + * - Add its new weight to cfs_rq->load.weight
> + */
> + if (!update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH))
> + return false;
>
> +
> + update_cfs_group(se);
> + return true;
> +}
> +
> static void
> enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> {
> @@ -3896,16 +3917,6 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> if (renorm && !curr)
> se->vruntime += cfs_rq->min_vruntime;
>
> - /*
> - * When enqueuing a sched_entity, we must:
> - * - Update loads to have both entity and cfs_rq synced with now.
> - * - Add its load to cfs_rq->runnable_avg
> - * - For group_entity, update its weight to reflect the new share of
> - * its group cfs_rq
> - * - Add its new weight to cfs_rq->load.weight
> - */
> - update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
> - update_cfs_group(se);
> enqueue_runnable_load_avg(cfs_rq, se);
> account_entity_enqueue(cfs_rq, se);
>
> @@ -3972,14 +3983,9 @@ static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
>
> static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
>
> -static void
> -dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> +static bool
> +dequeue_entity_groups(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> {
> - /*
> - * Update run-time statistics of the 'current'.
> - */
> - update_curr(cfs_rq);
> -
> /*
> * When dequeuing a sched_entity, we must:
> * - Update loads to have both entity and cfs_rq synced with now.
> @@ -3988,7 +3994,21 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> * - For group entity, update its weight to reflect the new share
> * of its group cfs_rq.
> */
> - update_load_avg(cfs_rq, se, UPDATE_TG);
> + if (!update_load_avg(cfs_rq, se, UPDATE_TG))
> + return false;
> + update_cfs_group(se);
> +
> + return true;
> +}
> +
> +static void
> +dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> +{
> + /*
> + * Update run-time statistics of the 'current'.
> + */
> + update_curr(cfs_rq);
> +
> dequeue_runnable_load_avg(cfs_rq, se);
>
> update_stats_dequeue(cfs_rq, se, flags);
> @@ -4012,8 +4032,6 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> /* return excess runtime on last dequeue */
> return_cfs_rq_runtime(cfs_rq);
>
> - update_cfs_group(se);
> -
> /*
> * Now advance min_vruntime if @se was the entity holding it back,
> * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
> @@ -5178,6 +5196,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
> if (se->on_rq)
> break;
> cfs_rq = cfs_rq_of(se);
> + enqueue_entity_groups(cfs_rq, se, flags);
> enqueue_entity(cfs_rq, se, flags);
>
> /*
> @@ -5260,6 +5279,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>
> for_each_sched_entity(se) {
> cfs_rq = cfs_rq_of(se);
> + dequeue_entity_groups(cfs_rq, se, flags);
> dequeue_entity(cfs_rq, se, flags);
>
> /*
> --
> 2.20.1
>
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