From: Vincent Guittot <vincent.guittot@linaro.org>
To: Rik van Riel <riel@surriel.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Phil Auld <pauld@redhat.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Quentin Perret <quentin.perret@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Morten Rasmussen <Morten.Rasmussen@arm.com>,
Hillf Danton <hdanton@sina.com>
Subject: Re: [PATCH v3 09/10] sched/fair: use load instead of runnable load in wakeup path
Date: Mon, 7 Oct 2019 17:27:10 +0200 [thread overview]
Message-ID: <CAKfTPtA763zLxToVJpOCKc8TAgD3aZwpwhMZbbzrKiok+UHFaA@mail.gmail.com> (raw)
In-Reply-To: <bc879bcb34f089e5888f6721aa2365f0832b69da.camel@surriel.com>
On Mon, 7 Oct 2019 at 17:14, Rik van Riel <riel@surriel.com> wrote:
>
> On Thu, 2019-09-19 at 09:33 +0200, Vincent Guittot wrote:
> > runnable load has been introduced to take into account the case where
> > blocked load biases the wake up path which may end to select an
> > overloaded
> > CPU with a large number of runnable tasks instead of an underutilized
> > CPU with a huge blocked load.
> >
> > Tha wake up path now starts to looks for idle CPUs before comparing
> > runnable load and it's worth aligning the wake up path with the
> > load_balance.
> >
> > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
>
> On a single socket system, patches 9 & 10 have the
> result of driving a woken up task (when wake_wide is
> true) to the CPU core with the lowest blocked load,
> even when there is an idle core the task could run on
> right now.
>
> With the whole series applied, I see a 1-2% regression
> in CPU use due to that issue.
>
> With only patches 1-8 applied, I see a 1% improvement in
> CPU use for that same workload.
Thanks for testing.
patch 8-9 have just replaced runnable load by blocked load and then
removed the duplicated metrics in find_idlest_group.
I'm preparing an additional patch that reworks find_idlest_group() to
behave similarly to find_busiest_group(). It gathers statistics what
it already does, then classifies the groups and finally selects the
idlest one. This should fix the problem that you mentioned above when
it selects a group with lowest blocked load whereas there are idle
cpus in another group with high blocked load.
>
> Given that it looks like select_idle_sibling and
> find_idlest_group_cpu do roughly the same thing, I
> wonder if it is enough to simply add an additional
> test to find_idlest_group to have it return the
> LLC sg, if it is called on the LLC sd on a single
> socket system.
That make sense to me
>
> That way find_idlest_group_cpu can still find an
> idle core like it does today.
>
> Does that seem like a reasonable thing?
That's worth testing
>
> I can run tests with that :)
>
> --
> All Rights Reversed.
next prev parent reply other threads:[~2019-10-07 15:27 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-19 7:33 [PATCH v3 0/8] sched/fair: rework the CFS load balance Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 01/10] sched/fair: clean up asym packing Vincent Guittot
2019-09-27 23:57 ` Rik van Riel
2019-09-19 7:33 ` [PATCH v3 02/10] sched/fair: rename sum_nr_running to sum_h_nr_running Vincent Guittot
2019-09-27 23:59 ` Rik van Riel
2019-10-01 17:11 ` Valentin Schneider
2019-09-19 7:33 ` [PATCH v3 03/10] sched/fair: remove meaningless imbalance calculation Vincent Guittot
2019-09-28 0:05 ` Rik van Riel
2019-10-01 17:12 ` Valentin Schneider
2019-10-02 6:28 ` Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 04/10] sched/fair: rework load_balance Vincent Guittot
2019-09-30 1:12 ` Rik van Riel
2019-09-30 7:44 ` Vincent Guittot
2019-09-30 16:24 ` Dietmar Eggemann
2019-10-01 8:14 ` Vincent Guittot
2019-10-01 16:52 ` Dietmar Eggemann
2019-10-02 6:44 ` Vincent Guittot
2019-10-02 9:21 ` Dietmar Eggemann
2019-10-08 13:02 ` Peter Zijlstra
2019-10-02 8:23 ` Vincent Guittot
2019-10-02 9:24 ` Dietmar Eggemann
2019-10-01 8:15 ` Dietmar Eggemann
2019-10-01 9:14 ` Vincent Guittot
2019-10-01 16:57 ` Dietmar Eggemann
2019-10-01 17:47 ` Valentin Schneider
2019-10-02 8:30 ` Vincent Guittot
2019-10-02 10:47 ` Valentin Schneider
2019-10-08 14:16 ` Peter Zijlstra
2019-10-08 14:34 ` Valentin Schneider
2019-10-08 15:30 ` Vincent Guittot
2019-10-08 15:48 ` Valentin Schneider
2019-10-08 17:39 ` Peter Zijlstra
2019-10-08 18:45 ` Vincent Guittot
2019-10-08 16:33 ` Peter Zijlstra
2019-10-08 16:39 ` Valentin Schneider
2019-10-08 17:36 ` Valentin Schneider
2019-10-08 17:55 ` Peter Zijlstra
2019-10-08 18:47 ` Vincent Guittot
2019-10-16 7:21 ` Parth Shah
2019-10-16 11:56 ` Vincent Guittot
2019-10-18 5:34 ` Parth Shah
2019-09-19 7:33 ` [PATCH v3 05/10] sched/fair: use rq->nr_running when balancing load Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 06/10] sched/fair: use load instead of runnable load in load_balance Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 07/10] sched/fair: evenly spread tasks when not overloaded Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 08/10] sched/fair: use utilization to select misfit task Vincent Guittot
2019-10-01 17:12 ` Valentin Schneider
2019-09-19 7:33 ` [PATCH v3 09/10] sched/fair: use load instead of runnable load in wakeup path Vincent Guittot
2019-10-07 15:14 ` Rik van Riel
2019-10-07 15:27 ` Vincent Guittot [this message]
2019-10-07 18:06 ` Rik van Riel
2019-09-19 7:33 ` [PATCH v3 10/10] sched/fair: optimize find_idlest_group Vincent Guittot
2019-10-08 14:32 ` [PATCH v3 0/8] sched/fair: rework the CFS load balance Phil Auld
2019-10-08 15:53 ` Vincent Guittot
2019-10-09 19:33 ` Phil Auld
2019-10-10 8:20 ` Vincent Guittot
2019-10-16 7:21 ` Parth Shah
2019-10-16 11:51 ` Vincent Guittot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAKfTPtA763zLxToVJpOCKc8TAgD3aZwpwhMZbbzrKiok+UHFaA@mail.gmail.com \
--to=vincent.guittot@linaro.org \
--cc=Morten.Rasmussen@arm.com \
--cc=dietmar.eggemann@arm.com \
--cc=hdanton@sina.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pauld@redhat.com \
--cc=peterz@infradead.org \
--cc=quentin.perret@arm.com \
--cc=riel@surriel.com \
--cc=srikar@linux.vnet.ibm.com \
--cc=valentin.schneider@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).