From: Peter Zijlstra <peterz@infradead.org>
To: Luis Machado <luis.machado@arm.com>
Cc: mingo@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, vschneid@redhat.com,
linux-kernel@vger.kernel.org, kprateek.nayak@amd.com,
wuyun.abel@bytedance.com, tglx@linutronix.de, efault@gmx.de,
nd <nd@arm.com>, John Stultz <jstultz@google.com>
Subject: Re: [RFC][PATCH 08/10] sched/fair: Implement delayed dequeue
Date: Fri, 26 Apr 2024 11:36:57 +0200 [thread overview]
Message-ID: <20240426093657.GJ12673@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20240426093241.GI12673@noisy.programming.kicks-ass.net>
On Fri, Apr 26, 2024 at 11:32:41AM +0200, Peter Zijlstra wrote:
> On Thu, Apr 25, 2024 at 01:49:49PM +0200, Peter Zijlstra wrote:
> > On Thu, Apr 25, 2024 at 12:42:20PM +0200, Peter Zijlstra wrote:
> >
> > > > I wonder if the delayed dequeue logic is having an unwanted effect on the calculation of
> > > > utilization/load of the runqueue and, as a consequence, we're scheduling things to run on
> > > > higher OPP's in the big cores, leading to poor decisions for energy efficiency.
> > >
> > > Notably util_est_update() gets delayed. Given we don't actually do an
> > > enqueue when a delayed task gets woken, it didn't seem to make sense to
> > > update that sooner.
> >
> > The PELT runnable values will be inflated because of delayed dequeue.
> > cpu_util() uses those in the @boost case, and as such this can indeed
> > affect things.
> >
> > This can also slightly affect the cgroup case, but since the delay goes
> > away as contention goes away, and the cgroup case must already assume
> > worst case overlap, this seems limited.
> >
> > /me goes ponder things moar.
>
> First order approximation of a fix would be something like the totally
> untested below I suppose...
>
> ---
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index cfd1fd188d29..f3f70b5adca0 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5391,6 +5391,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> if (cfs_rq->next == se)
> cfs_rq->next = NULL;
> se->sched_delayed = 1;
> + update_load_avg(cfs_rq, se, 0);
> return false;
> }
> }
> @@ -6817,6 +6818,7 @@ requeue_delayed_entity(struct sched_entity *se)
> }
>
> se->sched_delayed = 0;
> + update_load_avg(qcfs_rq, se, 0);
Compiler demands this ^^^^^ be cfs_rq instead ;-) brown_paper_bags--;
> }
>
> /*
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index d07a3b98f1fb..d16529613123 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -810,6 +810,9 @@ static inline void se_update_runnable(struct sched_entity *se)
>
> static inline long se_runnable(struct sched_entity *se)
> {
> + if (se->sched_delayed)
> + return false;
> +
> if (entity_is_task(se))
> return !!se->on_rq;
> else
> @@ -823,6 +826,9 @@ static inline void se_update_runnable(struct sched_entity *se) {}
>
> static inline long se_runnable(struct sched_entity *se)
> {
> + if (se->sched_delayed)
> + return false;
> +
> return !!se->on_rq;
> }
> #endif
next prev parent reply other threads:[~2024-04-26 9:37 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-05 10:27 [RFC][PATCH 00/10] sched/fair: Complete EEVDF Peter Zijlstra
2024-04-05 10:27 ` [RFC][PATCH 01/10] sched/eevdf: Add feature comments Peter Zijlstra
2024-04-05 10:27 ` [RFC][PATCH 02/10] sched/eevdf: Remove min_vruntime_copy Peter Zijlstra
2024-04-05 10:27 ` [RFC][PATCH 03/10] sched/fair: Cleanup pick_task_fair() vs throttle Peter Zijlstra
2024-04-05 21:11 ` Benjamin Segall
2024-04-05 10:27 ` [RFC][PATCH 04/10] sched/fair: Cleanup pick_task_fair()s curr Peter Zijlstra
2024-04-05 10:27 ` [RFC][PATCH 05/10] sched/fair: Unify pick_{,next_}_task_fair() Peter Zijlstra
2024-04-06 2:20 ` Mike Galbraith
2024-04-05 10:28 ` [RFC][PATCH 06/10] sched: Allow sched_class::dequeue_task() to fail Peter Zijlstra
2024-04-05 10:28 ` [RFC][PATCH 07/10] sched/fair: Re-organize dequeue_task_fair() Peter Zijlstra
2024-04-05 10:28 ` [RFC][PATCH 08/10] sched/fair: Implement delayed dequeue Peter Zijlstra
2024-04-06 9:23 ` Chen Yu
2024-04-08 9:06 ` Peter Zijlstra
2024-04-11 1:32 ` Yan-Jie Wang
2024-04-25 10:25 ` Peter Zijlstra
2024-04-12 10:42 ` K Prateek Nayak
2024-04-15 10:56 ` Mike Galbraith
2024-04-16 3:18 ` K Prateek Nayak
2024-04-16 5:36 ` Mike Galbraith
2024-04-18 16:24 ` Mike Galbraith
2024-04-18 17:08 ` K Prateek Nayak
2024-04-24 15:20 ` Peter Zijlstra
2024-04-25 11:28 ` Peter Zijlstra
2024-04-26 10:56 ` Peter Zijlstra
2024-04-26 11:16 ` Peter Zijlstra
2024-04-26 16:03 ` Mike Galbraith
2024-04-27 6:42 ` Mike Galbraith
2024-04-28 16:32 ` Mike Galbraith
2024-04-29 12:14 ` Peter Zijlstra
2024-04-15 17:07 ` Luis Machado
2024-04-24 15:15 ` Luis Machado
2024-04-25 10:42 ` Peter Zijlstra
2024-04-25 11:49 ` Peter Zijlstra
2024-04-26 9:32 ` Peter Zijlstra
2024-04-26 9:36 ` Peter Zijlstra [this message]
2024-04-26 10:16 ` Luis Machado
2024-04-29 14:33 ` Luis Machado
2024-05-02 10:26 ` Luis Machado
2024-05-10 14:49 ` Luis Machado
2024-05-15 9:36 ` Peter Zijlstra
2024-05-15 11:48 ` Peter Zijlstra
2024-05-15 18:03 ` Mike Galbraith
2024-04-26 10:15 ` Luis Machado
2024-04-20 5:57 ` Mike Galbraith
2024-04-22 13:13 ` Tobias Huschle
2024-04-05 10:28 ` [RFC][PATCH 09/10] sched/eevdf: Allow shorter slices to wakeup-preempt Peter Zijlstra
2024-04-05 10:28 ` [RFC][PATCH 10/10] sched/eevdf: Use sched_attr::sched_runtime to set request/slice suggestion Peter Zijlstra
2024-04-06 8:16 ` Hillf Danton
2024-05-07 5:34 ` Mike Galbraith
2024-05-15 10:13 ` Peter Zijlstra
2024-05-07 15:15 ` Chen Yu
2024-05-08 13:52 ` Mike Galbraith
2024-05-09 3:48 ` Chen Yu
2024-05-09 5:00 ` Mike Galbraith
2024-05-13 4:07 ` K Prateek Nayak
2024-05-14 9:18 ` Chen Yu
2024-05-14 15:23 ` K Prateek Nayak
2024-05-14 16:15 ` Chen Yu
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