From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Joel Fernandes <joel@joelfernandes.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Paul McKenney <paulmck@kernel.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Qais Yousef <qais.yousef@arm.com>,
Ben Segall <bsegall@google.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>, Mel Gorman <mgorman@suse.de>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH] sched/fair: Rate limit calls to update_blocked_averages() for NOHZ
Date: Mon, 25 Jan 2021 18:53:45 +0100 [thread overview]
Message-ID: <8db5ebd3-4e5c-cd7e-e0cb-dc86c3cafb5c@arm.com> (raw)
In-Reply-To: <CAKfTPtA7Fte3WWw1=-BaNX-fpfEeWicUOEgfzJsgCTcygzZTQA@mail.gmail.com>
On 25/01/2021 18:30, Vincent Guittot wrote:
> On Mon, 25 Jan 2021 at 11:45, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote:
>>
>> On 22/01/2021 20:10, Joel Fernandes wrote:
>>> Hi Vincent,
>>>
>>> Thanks for reply. Please see the replies below:
>>>
>>> On Fri, Jan 22, 2021 at 05:56:22PM +0100, Vincent Guittot wrote:
>>>> On Fri, 22 Jan 2021 at 16:46, Joel Fernandes (Google)
>>>> <joel@joelfernandes.org> wrote:
[...]
>> If I understood you correctly, you want to avoid these frequent calls
>> to update_blocked_averages() here to further avoid invoking sched_util
>> via update_blocked_averages() -> cpufreq_update_util() (since 'decayed'
>> is set) very often in your setup.
>
> So It's not clear if the problem that joel wants to raise, is about:
> - the running time of update_blocked_averages
> - the running time of the cpufreq_update_util which is called because
> utilization has decayed during the update of blocked load
> - the wake up latency because of newly_idle lb
Pretty much so.
IIRC his interest is driven by the fact that he saw much less activity
in newly_idle lb and therefore cpufreq_update_util on a system with the
same kernel and userspace but with less CPUs (i.e. also smaller
frequency domains) and less cgroups (with blocked load) and started
wondering why.
I assume that since he understands this environment now much better, he
should be able to come up with better test numbers to show if there is a
performance issue on his 2+6 DynamIQ system and if yes, where exactly in
this code path.
next prev parent reply other threads:[~2021-01-25 18:15 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-22 15:46 [PATCH] sched/fair: Rate limit calls to update_blocked_averages() for NOHZ Joel Fernandes (Google)
2021-01-22 16:56 ` Vincent Guittot
2021-01-22 18:39 ` Qais Yousef
2021-01-22 19:14 ` Joel Fernandes
2021-01-25 13:23 ` Vincent Guittot
2021-01-26 16:36 ` Qais Yousef
2021-01-22 19:10 ` Joel Fernandes
2021-01-25 10:44 ` Dietmar Eggemann
2021-01-25 17:30 ` Vincent Guittot
2021-01-25 17:53 ` Dietmar Eggemann [this message]
2021-01-25 14:42 ` Vincent Guittot
2021-01-27 18:43 ` Joel Fernandes
2021-01-28 13:57 ` Vincent Guittot
2021-01-28 15:09 ` Joel Fernandes
2021-01-28 16:57 ` Qais Yousef
[not found] ` <CAKfTPtBvwm9vZb5C=2oTF6N-Ht6Rvip4Lv18yi7O3G8e-_ZWdg@mail.gmail.com>
2021-01-29 17:27 ` Vincent Guittot
2021-02-03 11:54 ` Dietmar Eggemann
2021-02-03 13:12 ` Vincent Guittot
2021-02-04 9:47 ` Dietmar Eggemann
2021-02-03 17:09 ` Qais Yousef
2021-02-03 17:35 ` Vincent Guittot
2021-02-04 10:45 ` Qais Yousef
2021-02-03 19:56 ` Joel Fernandes
2021-03-23 21:37 ` Tim Chen
2021-03-24 13:44 ` Vincent Guittot
2021-03-24 16:05 ` Tim Chen
2021-04-07 14:02 ` Vincent Guittot
2021-04-07 17:19 ` Tim Chen
2021-04-08 14:51 ` Vincent Guittot
2021-04-08 23:05 ` Tim Chen
2021-04-09 15:26 ` Vincent Guittot
2021-04-09 17:59 ` Tim Chen
2021-05-10 21:59 ` Tim Chen
2021-05-11 15:25 ` Vincent Guittot
2021-05-11 17:25 ` Tim Chen
2021-05-11 17:56 ` Vincent Guittot
2021-05-12 13:59 ` Qais Yousef
2021-05-13 18:45 ` Tim Chen
2021-05-17 16:14 ` Qais Yousef
2021-06-11 20:00 ` Tim Chen
2021-06-18 10:28 ` Vincent Guittot
2021-06-18 16:14 ` Tim Chen
2021-06-25 8:50 ` Vincent Guittot
2021-02-01 15:13 ` Joel Fernandes
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