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SubjectRe: [PATCH] proc: Add RLIMIT_RTTIME to /proc/<pid>/limits
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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'.




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