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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Michael Kerrisk <mtk.manpages@googlemail.com>
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: Thu, 28 Feb 2008 16:50:21 +0100	[thread overview]
Message-ID: <1204213821.12120.15.camel@twins> (raw)
In-Reply-To: <cfd18e0f0802280744q18ccad3at3c88bac166806118@mail.gmail.com>


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.

> Also, is this limit per-thread or per-process?  I assume the latter --
> but can you confirm please.

Per process. Requests have been made to allow for per thread, but
rlimits are not.

Its really not meant as a fine-grained deadline notification mechanism,
we have posix timers for that, but as a watchdog to ensure we behave
'well'.



  reply	other threads:[~2008-02-28 15:50 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 [this message]
2008-04-11  7:38           ` Michael Kerrisk
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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