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From: "Michael Kerrisk" <mtk.manpages@googlemail.com>
To: "Peter Zijlstra" <a.p.zijlstra@chello.nl>
Cc: "Michael Kerrisk" <mtk.manpages@gmail.com>,
	"Eugene Teo" <eugeneteo@kernel.sg>,
	linux-kernel@vger.kernel.org,
	"Neil Horman" <nhorman@tuxdriver.com>,
	"Ingo Molnar" <mingo@elte.hu>
Subject: Re: [PATCH] proc: Add RLIMIT_RTTIME to /proc/<pid>/limits
Date: Fri, 11 Apr 2008 09:38:09 +0200	[thread overview]
Message-ID: <cfd18e0f0804110038q3b7740c9q1a96858d9531ab92@mail.gmail.com> (raw)
In-Reply-To: <1204213821.12120.15.camel@twins>

On Thu, Feb 28, 2008 at 5:50 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
>
> On Thu, 2008-02-28 at 16:44 +0100, Michael Kerrisk wrote:
> > Peter,
> >
> > Thanks for the text.
> >
> > On Thu, Feb 28, 2008 at 4:21 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> > >
> > >  On Thu, 2008-02-28 at 16:12 +0100, Michael Kerrisk wrote:
> > >  > Peter,
> > >  >
> > >  > Could you please provide some text describing RLIMIT_RTTIMEfor the
> > >  > getrlimit.2 man page.
> > >
> > >  The rlimit sets a timeout in [us] for SCHED_RR and SCHED_FIFO tasks.
> > >  This time is measured between sleeps, so a schedule in RR or a
> > >  preemption in either is not a sleep - the task needs to be dequeued and
> > >  enqueued for the timer to reset.
> >
> > Just to clarify: sleep here means a call to some blocking syscall
> > (e.g., nanosleep(), read(), select(), etc.), right?  Is there anything
> > else that falls under the category of "sleep"?  What about a call to
> > sched_yield() where the process explicitly lets go of the CPU?
>
> Yes, and yes, others would be blocking on futexes and the like.

Peter,

I've been testing this patch.  Above you seemed to be saying that
doing a sched_yield() would be equivalent to a sleep, causing the rt
counter to be reset to zero.  Howver, the results I'm seeing suggest
that a sched_yield() does not cause the counter to be reset to zero
(i.e., despite calling sched_yield() at frequent intervals, the
process still encounters the RLIM_RTTIME soft limit and gets SIGXCPU).
 Can you comment?

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:[~2008-04-11  7:38 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-08 14:59 Eugene Teo
2008-02-08 15:10 ` Peter Zijlstra
2008-02-28 15:12   ` Michael Kerrisk
2008-02-28 15:21     ` Peter Zijlstra
2008-02-28 15:44       ` Michael Kerrisk
2008-02-28 15:50         ` Peter Zijlstra
2008-04-11  7:38           ` Michael Kerrisk [this message]
2008-04-11  7:45             ` Peter Zijlstra
2008-04-11  8:01               ` Michael Kerrisk
2008-02-29 12:32       ` Neil Horman
2008-04-11  8:56       ` Michael Kerrisk
2008-04-11  9:01         ` Peter Zijlstra
2008-04-11  9:16           ` Michael Kerrisk
2008-04-11  9:21             ` Peter Zijlstra
2008-04-11  9:27               ` Michael Kerrisk
2008-04-11  9:32                 ` Peter Zijlstra
2008-04-11  9:38                   ` Michael Kerrisk
2008-04-18 16:52                     ` RLIMIT_RTTIME documentation for getrlimit.2 Michael Kerrisk
2008-04-28 11:44                       ` Michael Kerrisk
2008-04-28 12:09                         ` Peter Zijlstra
2008-04-28 12:14                           ` Michael Kerrisk

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