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From: Frederic Weisbecker <fweisbec@gmail.com>
To: Mike Galbraith <efault@gmx.de>
Cc: Rik van Riel <riel@redhat.com>,
	Luiz Capitulino <lcapitulino@redhat.com>,
	Wanpeng Li <kernellwp@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [BUG nohz]: wrong user and system time accounting
Date: Mon, 3 Apr 2017 16:40:49 +0200	[thread overview]
Message-ID: <20170403144047.GA3820@lerouge> (raw)
In-Reply-To: <1490880922.4702.66.camel@gmx.de>

On Thu, Mar 30, 2017 at 03:35:22PM +0200, Mike Galbraith wrote:
> On Thu, 2017-03-30 at 09:02 -0400, Rik van Riel wrote:
> > On Thu, 2017-03-30 at 14:51 +0200, Frederic Weisbecker wrote:
> 
> > > Also, why does it raise power consumption issues?
> > 
> > On a system without either nohz_full or nohz idle
> > mode, skewed ticks result in CPU cores waking up
> > at different times, and keeping an idle system
> > consuming power for more time than it would if all
> > the ticks happened simultaneously.
> 
> And if your server farm is mostly idle, that power savings may delay
> your bankruptcy proceedings by a whole microsecond ;-)
> 
> Or more seriously, what skew does do on boxen of size X today is
> something for perf to say.  At the time, removal was very bad for my 8
> socket box, and allegedly caused huge SGI beasts in horrific pain.

I see.
Nohz_full is already bad for powersavings anyway. CPU 0 always ticks :-)

  reply	other threads:[~2017-04-03 14:40 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-23 20:55 [BUG nohz]: wrong user and system time accounting Luiz Capitulino
2017-03-24  0:56 ` Rik van Riel
2017-03-24  1:05   ` Luiz Capitulino
2017-03-24  1:08     ` Rik van Riel
2017-03-24  1:39       ` Luiz Capitulino
2017-03-27  5:33   ` lkml
2017-03-24  1:52 ` Wanpeng Li
2017-03-24  3:56   ` Luiz Capitulino
2017-03-27  1:56 ` Wanpeng Li
2017-03-27 17:35   ` Rik van Riel
2017-03-28  7:19     ` Wanpeng Li
     [not found]     ` <20170328132406.7d23579c@redhat.com>
     [not found]       ` <20170328161454.4a5d9e8b@redhat.com>
2017-03-28 21:01         ` Rik van Riel
2017-03-28 21:26           ` Luiz Capitulino
2017-03-29  9:56             ` Wanpeng Li
2017-03-29 12:56               ` Frederic Weisbecker
2017-03-28 21:24         ` Rik van Riel
2017-03-28 21:30           ` Luiz Capitulino
     [not found]       ` <20170329131656.1d6cb743@redhat.com>
2017-03-29 20:08         ` Rik van Riel
2017-03-29 22:54           ` Frederic Weisbecker
2017-03-30 12:57             ` Rik van Riel
2017-03-30  1:58           ` Wanpeng Li
2017-03-30 12:40             ` Frederic Weisbecker
2017-03-30 13:19               ` Mike Galbraith
2017-03-30  4:27           ` Mike Galbraith
2017-03-30  6:47             ` Wanpeng Li
2017-03-30 11:52               ` Wanpeng Li
2017-03-30 12:33                 ` Mike Galbraith
2017-03-30 13:38               ` Frederic Weisbecker
2017-03-30 13:59                 ` Wanpeng Li
2017-03-30 14:18                   ` Frederic Weisbecker
2017-03-30 21:25                     ` Luiz Capitulino
2017-03-31 20:09                       ` Luiz Capitulino
2017-03-31 23:24                         ` Frederic Weisbecker
2017-04-01  3:11                           ` Luiz Capitulino
2017-04-03 15:23                             ` Frederic Weisbecker
2017-04-03 19:06                               ` Luiz Capitulino
2017-04-04 17:36                                 ` Luiz Capitulino
2017-04-05 14:26                                   ` Rik van Riel
2017-04-11 11:03                 ` Wanpeng Li
2017-04-11 11:36                   ` Peter Zijlstra
2017-04-11 11:43                     ` Wanpeng Li
2017-04-11 14:22               ` Thomas Gleixner
2017-04-12 13:18                 ` Frederic Weisbecker
2017-04-12 14:57                   ` Thomas Gleixner
2017-04-12 15:14                     ` Frederic Weisbecker
2017-04-13  4:31                     ` Wanpeng Li
2017-04-13 13:32                       ` Frederic Weisbecker
2017-05-02 10:01                         ` Wanpeng Li
2017-05-15  8:17                           ` Wanpeng Li
2017-06-29 17:22                             ` Frederic Weisbecker
2017-03-30 12:51             ` Frederic Weisbecker
2017-03-30 13:02               ` Rik van Riel
2017-03-30 13:35                 ` Mike Galbraith
2017-04-03 14:40                   ` Frederic Weisbecker [this message]
2017-04-04  7:32                     ` Mike Galbraith
2017-03-30 13:44                 ` Frederic Weisbecker
     [not found]         ` <20170329221700.GB23895@lerouge>
2017-03-29 22:46           ` Wanpeng Li
2017-03-30  2:14             ` Luiz Capitulino
2017-03-30 12:27               ` Wanpeng Li
2017-03-27 18:38   ` Luiz Capitulino
2017-03-28  5:28     ` Wanpeng Li
2017-03-28 13:44       ` Luiz Capitulino
2017-03-29 13:04 ` Frederic Weisbecker
2017-03-29 13:14   ` Rik van Riel
2017-03-29 13:23     ` Luiz Capitulino
2017-03-29 21:12       ` Frederic Weisbecker
2017-03-30  1:48         ` Luiz Capitulino

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