From: Juri Lelli <juri.lelli@redhat.com>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
mingo@kernel.org, linux-kernel@vger.kernel.org,
luca.abeni@santannapisa.it, bristot@redhat.com,
balsini@android.com, dvyukov@google.com, tglx@linutronix.de,
vpillai@digitalocean.com, rostedt@goodmis.org
Subject: Re: [RFC][PATCH 12/13] sched/deadline: Introduce deadline servers
Date: Thu, 8 Aug 2019 11:27:44 +0200 [thread overview]
Message-ID: <20190808092744.GI29310@localhost.localdomain> (raw)
In-Reply-To: <99a8339d-8e06-bff8-284b-1829d0683a7a@arm.com>
On 08/08/19 10:57, Dietmar Eggemann wrote:
> On 8/8/19 10:46 AM, Juri Lelli wrote:
> > On 08/08/19 10:11, Dietmar Eggemann wrote:
> >> On 8/8/19 9:56 AM, Peter Zijlstra wrote:
> >>> On Wed, Aug 07, 2019 at 06:31:59PM +0200, Dietmar Eggemann wrote:
> >>>> On 7/26/19 4:54 PM, Peter Zijlstra wrote:
> >>>>>
> >>>>>
> >>>>> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> >>>>
> >>>> [...]
> >>>>
> >>>>> @@ -889,6 +891,8 @@ static void update_curr(struct cfs_rq *c
> >>>>> trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
> >>>>> cgroup_account_cputime(curtask, delta_exec);
> >>>>> account_group_exec_runtime(curtask, delta_exec);
> >>>>> + if (curtask->server)
> >>>>> + dl_server_update(curtask->server, delta_exec);
> >>>>> }
> >>>>
> >>>> I get a lockdep_assert_held(&rq->lock) related warning in start_dl_timer()
> >>>> when running the full stack.
> >>>
> >>> That would seem to imply a stale curtask->server value; the hunk below:
> >>>
> >>> --- a/kernel/sched/core.c
> >>> +++ b/kernel/sched/core.c
> >>> @@ -3756,8 +3756,11 @@ pick_next_task(struct rq *rq, struct tas
> >>>
> >>> for_each_class(class) {
> >>> p = class->pick_next_task(rq, NULL, NULL);
> >>> - if (p)
> >>> + if (p) {
> >>> + if (p->sched_class == class && p->server)
> >>> + p->server = NULL;
> >>> return p;
> >>> + }
> >>> }
> >>>
> >>>
> >>> Was supposed to clear p->server, but clearly something is going 'funny'.
> >>
> >> What about the fast path in pick_next_task()?
> >>
> >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> >> index bffe849b5a42..f1ea6ae16052 100644
> >> --- a/kernel/sched/core.c
> >> +++ b/kernel/sched/core.c
> >> @@ -3742,6 +3742,9 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
> >> if (unlikely(!p))
> >> p = idle_sched_class.pick_next_task(rq, prev, rf);
> >>
> >> + if (p->sched_class == &fair_sched_class && p->server)
> >> + p->server = NULL;
> >> +
> >
> > Hummm, but then who sets it back to the correct server. AFAIU
> > update_curr() needs a ->server to do the correct DL accounting?
>
> Ah, OK, this would kill the whole functionality ;-)
>
I'm thinking we could use &rq->fair_server. It seems to pass the point
we are discussing about, but then virt box becomes unresponsive (busy
loops).
next prev parent reply other threads:[~2019-08-08 9:27 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-26 14:54 [RFC][PATCH 00/13] SCHED_DEADLINE server infrastructure Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 01/13] sched/deadline: Impose global limits on sched_attr::sched_period Peter Zijlstra
2019-07-29 8:57 ` Juri Lelli
2019-07-29 11:45 ` Daniel Bristot de Oliveira
2019-08-02 17:21 ` Alessio Balsini
2019-08-05 11:53 ` Peter Zijlstra
2019-08-22 12:29 ` Alessio Balsini
2019-08-22 16:51 ` Peter Zijlstra
2019-08-31 14:41 ` Alessio Balsini
2019-09-02 9:16 ` Peter Zijlstra
2019-09-02 12:31 ` Peter Zijlstra
2019-09-04 10:16 ` Steven Rostedt
2019-09-04 11:30 ` Peter Zijlstra
2019-09-04 13:24 ` Joel Fernandes
2019-09-04 14:11 ` Will Deacon
2019-09-04 14:35 ` Joel Fernandes
2019-09-04 15:52 ` Peter Zijlstra
2019-10-23 17:17 ` [PATCH 4.4 4.9 4.14] loop: Add LOOP_SET_DIRECT_IO to compat ioctl Alessio Balsini
2019-10-23 17:22 ` Alessio Balsini
2019-10-25 0:17 ` Sasha Levin
2020-05-20 18:38 ` [RFC][PATCH 01/13] sched/deadline: Impose global limits on sched_attr::sched_period Juri Lelli
2020-05-21 13:45 ` Daniel Bristot de Oliveira
2020-06-16 12:21 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 02/13] stop_machine: Fix stop_cpus_in_progress ordering Peter Zijlstra
2019-07-30 13:16 ` Phil Auld
2019-07-30 13:22 ` Steven Rostedt
2019-07-26 14:54 ` [RFC][PATCH 03/13] sched: Fix kerneldoc comment for ia64_set_curr_task Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 04/13] sched/{rt,deadline}: Fix set_next_task vs pick_next_task Peter Zijlstra
2019-07-29 9:25 ` Juri Lelli
2019-07-29 11:15 ` Peter Zijlstra
2019-07-29 11:27 ` Juri Lelli
2019-07-29 13:04 ` Peter Zijlstra
2019-07-29 13:17 ` Juri Lelli
2019-07-29 14:40 ` Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 05/13] sched: Add task_struct pointer to sched_class::set_curr_task Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 06/13] sched/fair: Export newidle_balance() Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 07/13] sched: Allow put_prev_task() to drop rq->lock Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 08/13] sched: Rework pick_next_task() slow-path Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 09/13] sched: Unify runtime accounting across classes Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 10/13] sched/deadline: Collect sched_dl_entity initialization Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 11/13] sched/deadline: Move bandwidth accounting into {en,de}queue_dl_entity Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 12/13] sched/deadline: Introduce deadline servers Peter Zijlstra
2019-08-07 16:31 ` Dietmar Eggemann
2019-08-08 6:52 ` Juri Lelli
2019-08-08 7:52 ` Dietmar Eggemann
2019-08-08 7:56 ` Peter Zijlstra
2019-08-08 8:11 ` Dietmar Eggemann
2019-08-08 8:46 ` Juri Lelli
2019-08-08 8:57 ` Dietmar Eggemann
2019-08-08 9:27 ` Juri Lelli [this message]
2019-08-08 9:45 ` Juri Lelli
2019-08-30 11:24 ` Peter Zijlstra
2019-09-06 9:36 ` Juri Lelli
2019-08-08 10:31 ` Peter Zijlstra
2019-08-09 7:13 ` Juri Lelli
2019-08-08 6:59 ` Juri Lelli
2019-08-09 9:17 ` Dietmar Eggemann
2019-08-09 12:16 ` Juri Lelli
2019-07-26 14:54 ` [RFC][PATCH 13/13] sched/fair: Add trivial fair server Peter Zijlstra
2019-07-26 20:01 ` [RFC][PATCH 00/13] SCHED_DEADLINE server infrastructure luca abeni
2019-09-03 14:27 ` Alessio Balsini
2019-09-04 10:50 ` Juri Lelli
2019-09-04 11:32 ` Peter Zijlstra
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