All of lore.kernel.org
 help / color / mirror / Atom feed
From: Steven Rostedt <rostedt@goodmis.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
	Tony Lindgren <tony@atomide.com>, Mike Galbraith <efault@gmx.de>
Subject: Re: [RFC patch 1/2] sched: dynamically adapt granularity with nr_running
Date: Mon, 13 Sep 2010 11:39:28 -0400	[thread overview]
Message-ID: <1284392368.17152.44.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <20100913152514.GA8771@Krystal>

On Mon, 2010-09-13 at 11:25 -0400, Mathieu Desnoyers wrote:

> > > The more divs we put it, the more expensive it all becomes.
> > > 
> > 
> > What about:
> > 
> > 	if (delta_exec < sysctl_sched_min_granularity ||
> > 	    delta_exec < __sched_gran(cfs_rq->nr_running))
> > 
> > This way we avoid the div when delta_exec is less than the
> > min_granularity, and then we can do the div to perhaps avoid a needless
> > resched?
> 
> Please note that my patch does not even take the 32-bit div when there are less
> than 4 threads running on the system.
> 
> So I'm not at all sure we're trying to optimize an important case here.

If we have 5 threads running and hit this where delta_exec is <
sched_min_granularity, then we do have that div, right? Question is, how
often do we hit this condition where delta_exec is less while running
more that 4 threads?

-- Steve



  reply	other threads:[~2010-09-13 15:39 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-09-11 17:37 [RFC patch 0/2] sched: dynamically adapt granularity with nr_running Mathieu Desnoyers
2010-09-11 17:37 ` [RFC patch 1/2] " Mathieu Desnoyers
2010-09-11 18:57   ` Peter Zijlstra
2010-09-11 19:21     ` Linus Torvalds
2010-09-11 20:36       ` Peter Zijlstra
2010-09-11 20:45         ` Peter Zijlstra
2010-09-11 20:52           ` Linus Torvalds
2010-09-12  9:07             ` Peter Zijlstra
2010-09-11 20:48         ` Linus Torvalds
2010-09-12  9:06           ` Peter Zijlstra
2010-09-12  9:14             ` Peter Zijlstra
2010-09-12 20:39               ` Mathieu Desnoyers
2010-09-13 12:54                 ` Peter Zijlstra
2010-09-12 20:34             ` Mathieu Desnoyers
2010-09-13 12:53               ` Peter Zijlstra
2010-09-13  4:35             ` Mike Galbraith
2010-09-13  8:41               ` Peter Zijlstra
2010-09-13 11:22                 ` Ingo Molnar
2010-09-13 13:52                 ` Steven Rostedt
2010-09-13 13:54                   ` Peter Zijlstra
2010-09-13 14:02                     ` Peter Zijlstra
2010-09-13 14:21                       ` Ingo Molnar
2010-09-11 20:52         ` Mathieu Desnoyers
2010-09-11 19:57     ` Mathieu Desnoyers
2010-09-12 10:41       ` Peter Zijlstra
2010-09-12 20:37         ` Mathieu Desnoyers
2010-09-13 12:53           ` Peter Zijlstra
2010-09-13 13:15             ` Peter Zijlstra
2010-09-13 13:56               ` Mathieu Desnoyers
2010-09-13 14:16                 ` Peter Zijlstra
2010-09-13 14:43                   ` Steven Rostedt
2010-09-13 15:25                     ` Mathieu Desnoyers
2010-09-13 15:39                       ` Steven Rostedt [this message]
2010-09-13 16:16                   ` [RFC PATCH] check_preempt_tick should not compare vruntime with wall time Mathieu Desnoyers
2010-09-13 16:36                     ` Linus Torvalds
2010-09-13 17:45                       ` Mathieu Desnoyers
2010-09-13 17:51                         ` Linus Torvalds
2010-09-13 18:01                           ` Mathieu Desnoyers
2010-09-13 18:10                           ` Steven Rostedt
2010-09-13 18:03                         ` Ingo Molnar
2010-09-13 18:19                           ` Mathieu Desnoyers
2010-09-13 18:23                             ` [PATCH] sched: Improve latencies under load by decreasing minimum scheduling granularity Ingo Molnar
2010-09-13 18:28                               ` Joe Perches
2010-09-13 19:44                               ` Linus Torvalds
2010-09-13 20:00                                 ` Ingo Molnar
2010-09-13 18:19                         ` [RFC PATCH] check_preempt_tick should not compare vruntime with wall time Ingo Molnar
2010-09-13 17:36                     ` Ingo Molnar
2010-09-13 17:56                       ` Mathieu Desnoyers
2010-09-14  2:10                     ` Mike Galbraith
2010-09-13 14:44                 ` [RFC patch 1/2] sched: dynamically adapt granularity with nr_running Mike Galbraith
     [not found]               ` <1284386179.10436.6.camel@marge.simson.net>
2010-09-13 15:53                 ` Peter Zijlstra
2010-09-13 18:04                   ` [RFC][PATCH] sched: Improve tick preemption Peter Zijlstra
2010-09-14  2:27                   ` [RFC patch 1/2] sched: dynamically adapt granularity with nr_running Mike Galbraith
2010-09-12  6:14   ` Ingo Molnar
2010-09-12  7:21     ` Mike Galbraith
2010-09-12 18:16       ` Mathieu Desnoyers
2010-09-13  4:13         ` Mike Galbraith
2010-09-13  6:41           ` Ingo Molnar
2010-09-13  7:08             ` Mike Galbraith
2010-09-13  7:35               ` Mike Galbraith
2010-09-13  8:35               ` Peter Zijlstra
2010-09-13  9:16                 ` Mike Galbraith
2010-09-13  9:37                   ` Peter Zijlstra
2010-09-13  9:50                     ` Mike Galbraith
2010-09-13  9:55                       ` Peter Zijlstra
2010-09-13 10:06                         ` Mike Galbraith
2010-09-13 10:45                         ` Peter Zijlstra
2010-09-13 11:43                           ` Peter Zijlstra
2010-09-13 11:49                             ` Peter Zijlstra
2010-09-13 12:32                             ` Mike Galbraith
2010-09-13 20:19             ` Mathieu Desnoyers
2010-09-13 20:56               ` Mathieu Desnoyers
2010-09-12 18:13     ` Mathieu Desnoyers
2010-09-12 23:44       ` Mathieu Desnoyers
2010-09-11 17:37 ` [RFC patch 2/2] sched: sleepers coarse granularity on wakeup Mathieu Desnoyers
2010-09-12 12:44 ` [RFC patch 0/2] sched: dynamically adapt granularity with nr_running Peter Zijlstra

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=1284392368.17152.44.camel@gandalf.stny.rr.com \
    --to=rostedt@goodmis.org \
    --cc=akpm@linux-foundation.org \
    --cc=efault@gmx.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mathieu.desnoyers@efficios.com \
    --cc=mingo@elte.hu \
    --cc=peterz@infradead.org \
    --cc=tglx@linutronix.de \
    --cc=tony@atomide.com \
    --cc=torvalds@linux-foundation.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.