linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Chris Mason <clm@fb.com>
To: Tejun Heo <tj@kernel.org>, Vincent Guittot <vincent.guittot@linaro.org>
Cc: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Mike Galbraith <efault@gmx.de>, Paul Turner <pjt@google.com>,
	<kernel-team@fb.com>
Subject: Re: [PATCH 2/2] sched/fair: Always propagate runnable_load_avg
Date: Tue, 25 Apr 2017 17:15:32 -0400	[thread overview]
Message-ID: <6248cdfe-c5d1-35f2-003b-3a260b5a94ea@fb.com> (raw)
In-Reply-To: <20170425204907.GA20255@wtj.duckdns.org>



On 04/25/2017 04:49 PM, Tejun Heo wrote:
> On Tue, Apr 25, 2017 at 11:49:41AM -0700, Tejun Heo wrote:
>> Will try that too.  I can't see why HT would change it because I see
>> single CPU queues misevaluated.  Just in case, you need to tune the
>> test params so that it doesn't load the machine too much and that
>> there are some non-CPU intensive workloads going on to purturb things
>> a bit.  Anyways, I'm gonna try disabling HT.
>
> It's finickier but after changing the duty cycle a bit, it reproduces
> w/ HT off.  I think the trick is setting the number of threads to the
> number of logical CPUs and tune -s/-c so that p99 starts climbing up.
> The following is from the root cgroup.

Since it's only measuring wakeup latency, schbench is best at exposing 
problems when the machine is just barely below saturated.  At 
saturation, everyone has to wait for the CPUs, and if we're relatively 
idle there's always a CPU to be found

There's schbench -a to try and find this magic tipping point, but I 
haven't found a great way to automate for every kind of machine yet (sorry).

-chris

  reply	other threads:[~2017-04-25 21:16 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-24 20:13 [RFC PATCHSET] sched/fair: fix load balancer behavior when cgroup is in use Tejun Heo
2017-04-24 20:14 ` [PATCH 1/2] sched/fair: Fix how load gets propagated from cfs_rq to its sched_entity Tejun Heo
2017-04-24 21:33   ` [PATCH v2 " Tejun Heo
2017-05-03 18:00     ` Peter Zijlstra
2017-05-03 21:45       ` Tejun Heo
2017-05-04  5:51         ` Peter Zijlstra
2017-05-04  6:21           ` Peter Zijlstra
2017-05-04  9:49             ` Dietmar Eggemann
2017-05-04 10:57               ` Peter Zijlstra
2017-05-04 17:39               ` Tejun Heo
2017-05-05 10:36                 ` Dietmar Eggemann
2017-05-04 10:26       ` Vincent Guittot
2017-04-25  8:35   ` [PATCH " Vincent Guittot
2017-04-25 18:12     ` Tejun Heo
2017-04-26 16:51       ` Vincent Guittot
2017-04-26 22:40         ` Tejun Heo
2017-04-27  7:00           ` Vincent Guittot
2017-05-01 14:17         ` Peter Zijlstra
2017-05-01 14:52           ` Peter Zijlstra
2017-05-01 21:56           ` Tejun Heo
2017-05-02  8:19             ` Peter Zijlstra
2017-05-02  8:30               ` Peter Zijlstra
2017-05-02 20:00                 ` Tejun Heo
2017-05-03  9:10                   ` Peter Zijlstra
2017-04-26 16:14   ` Vincent Guittot
2017-04-26 22:27     ` Tejun Heo
2017-04-27  8:59       ` Vincent Guittot
2017-04-28 17:46         ` Tejun Heo
2017-05-02  7:20           ` Vincent Guittot
2017-04-24 20:14 ` [PATCH 2/2] sched/fair: Always propagate runnable_load_avg Tejun Heo
2017-04-25  8:46   ` Vincent Guittot
2017-04-25  9:05     ` Vincent Guittot
2017-04-25 12:59       ` Vincent Guittot
2017-04-25 18:49         ` Tejun Heo
2017-04-25 20:49           ` Tejun Heo
2017-04-25 21:15             ` Chris Mason [this message]
2017-04-25 21:08           ` Tejun Heo
2017-04-26 10:21             ` Vincent Guittot
2017-04-27  0:30               ` Tejun Heo
2017-04-27  8:28                 ` Vincent Guittot
2017-04-28 16:14                   ` Tejun Heo
2017-05-02  6:56                     ` Vincent Guittot
2017-05-02 20:56                       ` Tejun Heo
2017-05-03  7:25                         ` Vincent Guittot
2017-05-03  7:54                           ` Vincent Guittot
2017-04-26 18:12   ` Vincent Guittot
2017-04-26 22:52     ` Tejun Heo
2017-04-27  8:29       ` Vincent Guittot
2017-04-28 20:33         ` Tejun Heo
2017-04-28 20:38           ` Tejun Heo
2017-05-01 15:56           ` Peter Zijlstra
2017-05-02 22:01             ` Tejun Heo
2017-05-02  7:18           ` Vincent Guittot
2017-05-02 13:26             ` Vincent Guittot
2017-05-02 22:37               ` Tejun Heo
2017-05-02 21:50             ` Tejun Heo
2017-05-03  7:34               ` Vincent Guittot
2017-05-03  9:37                 ` Peter Zijlstra
2017-05-03 10:37                   ` Vincent Guittot
2017-05-03 13:09                     ` Peter Zijlstra
2017-05-03 21:49                       ` Tejun Heo
2017-05-04  8:19                         ` Vincent Guittot
2017-05-04 17:43                           ` Tejun Heo
2017-05-04 19:02                             ` Vincent Guittot
2017-05-04 19:04                               ` Tejun Heo
2017-04-24 21:35 ` [PATCH 3/2] sched/fair: Skip __update_load_avg() on cfs_rq sched_entities Tejun Heo
2017-04-24 21:48   ` Peter Zijlstra
2017-04-24 22:54     ` Tejun Heo
2017-04-25 21:09   ` Tejun Heo

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=6248cdfe-c5d1-35f2-003b-3a260b5a94ea@fb.com \
    --to=clm@fb.com \
    --cc=efault@gmx.de \
    --cc=kernel-team@fb.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=pjt@google.com \
    --cc=tj@kernel.org \
    --cc=torvalds@linux-foundation.org \
    --cc=vincent.guittot@linaro.org \
    /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).