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From: Ingo Molnar <mingo@elte.hu>
To: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Arnd Bergmann <arnd@arndb.de>, Christoph Hellwig <hch@lst.de>,
	cbe-oss-dev@ozlabs.org, Jeremy Kerr <jk@ozlabs.org>,
	linux-kernel@vger.kernel.org
Subject: Re: SCHED_IDLE documentation
Date: Mon, 3 Mar 2008 10:24:22 +0100	[thread overview]
Message-ID: <20080303092422.GA18281@elte.hu> (raw)
In-Reply-To: <cfd18e0f0803030040l667dd2b7v6298e78c5b21bfec@mail.gmail.com>


* Michael Kerrisk <mtk.manpages@googlemail.com> wrote:

> On Mon, Mar 3, 2008 at 8:33 AM, Ingo Molnar <mingo@elte.hu> wrote:
> >
> > * Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > > If we don't have any man page, what is the actual definition of
> > > SCHED_IDLE anyway?
> >
> > it's rather simple: "it's a priority level even lower priority than nice
> > +19".
> 
> Some other questions whose answers may be worth including in the man page:
> 
> * When was SCHED_IDLE added?  (Actually, who added it?)

"git-blame include/linux/sched.h" gives you that information, it was 
added by me as part of CFS:

  commit 0e6aca43e08a62a48d6770e9a159dbec167bf4c6
  Author: Ingo Molnar <mingo@elte.hu>
  Date:   Mon Jul 9 18:51:57 2007 +0200

      sched: add SCHED_IDLE policy
 
> * Why was it added?  (What are the particular benefits of the new 
> sceuling class as opposed to using a very low nice value for 
> SCHED_OTHER?)

because some people wanted even lower priorities than what nice +19 
gave, and extending nice levels wasnt possible for ABI reasons.

> * What's the difference between SCHED_IDLE and SCHED_BATCH?

SCHED_BATCH can still have nice levels from -20 to +19, it is a modified 
SCHED_OTHER/SCHED_NORMAL for "throughput oriented" workloads.

SCHED_IDLE overrides the nice settings and it means a "super idle" 
workload.

	Ingo

  reply	other threads:[~2008-03-03  9:24 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1203376368.275756.252634247263.1.gpush@pokey>
     [not found] ` <200803030612.28039.arnd@arndb.de>
     [not found]   ` <20080303051719.GA26102@lst.de>
2008-03-03  6:21     ` Arnd Bergmann
2008-03-03  7:33       ` Ingo Molnar
2008-03-03  8:40         ` Michael Kerrisk
2008-03-03  9:24           ` Ingo Molnar [this message]
2008-03-03  9:31             ` Arnd Bergmann
2008-03-03 10:03               ` Michael Kerrisk
2008-03-03 10:04               ` Ingo Molnar
2008-03-03 10:12                 ` Michael Kerrisk
2008-03-03 10:07             ` Michael Kerrisk
2008-03-03 10:17               ` Ingo Molnar
2008-03-03 10:20                 ` Michael Kerrisk
2008-03-03 12:31             ` Michael Kerrisk
2008-03-03 12:52               ` Ingo Molnar
2008-03-03 14:06                 ` Michael Kerrisk
2008-03-04 11:11                   ` Peter Zijlstra
2008-03-05 15:19                     ` Michael Kerrisk
2008-03-03 14:42                 ` Michael Kerrisk
2008-03-05 15:02                   ` Michael Kerrisk

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