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From: "Michael Kerrisk" <mtk.manpages@googlemail.com>
To: "Ingo Molnar" <mingo@elte.hu>
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 11:12:52 +0100	[thread overview]
Message-ID: <cfd18e0f0803030212l3783567ek6ca058889873dfac@mail.gmail.com> (raw)
In-Reply-To: <20080303100418.GF18281@elte.hu>

On Mon, Mar 3, 2008 at 11:04 AM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Arnd Bergmann <arnd@arndb.de> wrote:
>
> > On Monday 03 March 2008, Ingo Molnar wrote:
> > > > * 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.
> >
> > Does that mean that a SCHED_IDLE task still runs some of the time if
> > you have a CPU hog running on +19, or can any other process starve the
> > SCHED_IDLE task?
>
> yes, even SCHED_IDLE tasks get some CPU time - so complete starvation
> should not be possible. We dont really want to define the exact amount
> of time they need. (we might want to change that in the future) But it
> will always be less prio than nice +19 :-) You can think of it as if it
> was "nice +30".
>
> > What happens if you have two SCHED_IDLE tasks on a single CPU, do they
> > get equal share, or will they just run as batch jobs?
>
> they get equal share.
>
> you can try it out too: if you have 2.6.23 or newer kernels then just
> pick up schedtool and use "schedtool -I" to run SCHED_IDLE tasks.

Thanks for the answers Ingo!

Cheers,

Michael

-- 
Michael Kerrisk
Maintainer of the Linux man-pages project
http://www.kernel.org/doc/man-pages/
Want to report a man-pages bug?  Look here:
http://www.kernel.org/doc/man-pages/reporting_bugs.html

  reply	other threads:[~2008-03-03 10:13 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
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 [this message]
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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