From: Vincent Guittot <vincent.guittot@linaro.org>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
linux-kernel <linux-kernel@vger.kernel.org>,
Phil Auld <pauld@redhat.com>, Parth Shah <parth@linux.ibm.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Hillf Danton <hdanton@sina.com>
Subject: Re: [PATCH v2 1/5] sched/fair: Reorder enqueue/dequeue_task_fair path
Date: Wed, 19 Feb 2020 17:26:11 +0100 [thread overview]
Message-ID: <CAKfTPtCbHb2X30gNqNp5sukrg9U-hC6rvWC0dj8d1DawNL4D3Q@mail.gmail.com> (raw)
In-Reply-To: <c18ab89e-d635-e370-6cbb-6015b404d906@arm.com>
On Wed, 19 Feb 2020 at 12:07, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote:
>
> On 18/02/2020 15:15, Vincent Guittot wrote:
> > On Tue, 18 Feb 2020 at 14:22, Peter Zijlstra <peterz@infradead.org> wrote:
> >>
> >> On Tue, Feb 18, 2020 at 01:37:37PM +0100, Dietmar Eggemann wrote:
> >>> On 14/02/2020 16:27, Vincent Guittot wrote:
> >>>> The walk through the cgroup hierarchy during the enqueue/dequeue of a task
> >>>> is split in 2 distinct parts for throttled cfs_rq without any added value
> >>>> but making code less readable.
> >>>>
> >>>> Change the code ordering such that everything related to a cfs_rq
> >>>> (throttled or not) will be done in the same loop.
> >>>>
> >>>> In addition, the same steps ordering is used when updating a cfs_rq:
> >>>> - update_load_avg
> >>>> - update_cfs_group
> >>>> - update *h_nr_running
> >>>
> >>> Is this code change really necessary? You pay with two extra goto's. We
> >>> still have the two for_each_sched_entity(se)'s because of 'if
> >>> (se->on_rq); break;'.
> >>
> >> IIRC he relies on the presented ordering in patch #5 -- adding the
> >> running_avg metric.
> >
> > Yes, that's the main reason, updating load_avg before h_nr_running
>
> My hunch is you refer to the new function:
>
> static inline void se_update_runnable(struct sched_entity *se)
> {
> if (!entity_is_task(se))
> se->runnable_weight = se->my_q->h_nr_running;
> }
>
> I don't see the dependency to the 'update_load_avg -> h_nr_running'
> order since it operates on se->my_q, not cfs_rq = cfs_rq_of(se), i.e.
> se->cfs_rq.
>
> What do I miss here?
update_load_avg() updates both se and cfs_rq so if you update
cfs_rq->h_nr_running before calling update_load_avg() like in the 2nd
for_each_sched_entity, you will update cfs_rq runnable_avg for the
past time slot with the new h_nr_running value instead of the previous
value.
next prev parent reply other threads:[~2020-02-19 16:26 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 15:27 [PATCH v2 0/5] remove runnable_load_avg and improve group_classify Vincent Guittot
2020-02-14 15:27 ` [PATCH v2 1/5] sched/fair: Reorder enqueue/dequeue_task_fair path Vincent Guittot
2020-02-18 12:37 ` Dietmar Eggemann
2020-02-18 13:22 ` Peter Zijlstra
2020-02-18 14:15 ` Vincent Guittot
2020-02-19 11:07 ` Dietmar Eggemann
2020-02-19 16:26 ` Vincent Guittot [this message]
2020-02-20 13:38 ` Dietmar Eggemann
[not found] ` <20200222152541.GA11669@geo.homenetwork>
2020-02-26 16:30 ` Vincent Guittot
2020-02-14 15:27 ` [PATCH v2 2/5] sched/numa: Replace runnable_load_avg by load_avg Vincent Guittot
2020-02-18 12:37 ` Dietmar Eggemann
2020-02-18 13:50 ` Mel Gorman
2020-02-18 14:17 ` Vincent Guittot
2020-02-18 14:42 ` Dietmar Eggemann
2020-02-18 14:54 ` Valentin Schneider
2020-02-18 15:33 ` Vincent Guittot
2020-02-18 15:38 ` Mel Gorman
2020-02-18 16:50 ` Valentin Schneider
2020-02-18 17:41 ` Mel Gorman
2020-02-18 17:54 ` Valentin Schneider
2020-02-18 16:51 ` Vincent Guittot
2020-02-14 15:27 ` [PATCH v2 3/5] sched/pelt: Remove unused runnable load average Vincent Guittot
2020-02-21 9:57 ` Dietmar Eggemann
2020-02-21 11:56 ` Vincent Guittot
2020-02-14 15:27 ` [PATCH v2 4/5] sched/pelt: Add a new runnable average signal Vincent Guittot
2020-02-18 14:54 ` Valentin Schneider
2020-02-18 15:12 ` Peter Zijlstra
2020-02-18 15:28 ` Vincent Guittot
2020-02-18 16:30 ` Valentin Schneider
2020-02-18 21:19 ` Valentin Schneider
2020-02-19 9:02 ` Vincent Guittot
2020-02-19 9:08 ` Mel Gorman
2020-02-19 12:55 ` [PATCH v3 " Vincent Guittot
2020-02-19 14:02 ` Mel Gorman
2020-02-19 20:10 ` Valentin Schneider
2020-02-20 14:36 ` Vincent Guittot
2020-02-20 16:11 ` Valentin Schneider
2020-02-21 8:56 ` Vincent Guittot
2020-02-24 15:57 ` Valentin Schneider
2020-02-21 9:04 ` Mel Gorman
2020-02-21 9:25 ` Vincent Guittot
2020-02-21 10:40 ` Mel Gorman
2020-02-21 13:28 ` Vincent Guittot
2020-02-20 15:04 ` Dietmar Eggemann
2020-02-21 9:44 ` Dietmar Eggemann
2020-02-21 11:47 ` Vincent Guittot
2020-02-14 15:27 ` [PATCH v2 5/5] sched/fair: Take into account runnable_avg to classify group Vincent Guittot
2020-02-15 21:58 ` [PATCH v2 0/5] remove runnable_load_avg and improve group_classify Mel Gorman
2020-02-21 9:58 ` Dietmar Eggemann
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