linux-kernel - Re: [PATCH] proc: Add RLIMIT_RTTIME to /proc/<pid>/limits

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Date:	Thu, 28 Feb 2008 16:44:16 +0100
From:	"Michael Kerrisk" <mtk.manpages@...glemail.com>
To:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Cc:	"Michael Kerrisk" <mtk.manpages@...il.com>,
	"Eugene Teo" <eugeneteo@...nel.sg>, linux-kernel@...r.kernel.org,
	"Neil Horman" <nhorman@...driver.com>,
	"Ingo Molnar" <mingo@...e.hu>
Subject: Re: [PATCH] proc: Add RLIMIT_RTTIME to /proc/<pid>/limits

Peter,

Thanks for the text.

On Thu, Feb 28, 2008 at 4:21 PM, Peter Zijlstra <a.p.zijlstra@...llo.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?

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

Cheers,

Michael

>  Upon reaching the cur limit we start giving SIGXCPU every second, upon
>  reaching the hard limit we give SIGKILL - matching RLIMIT_CPU.
>
>  Time is measured in tick granularity (for now).
>
>
>
>  > Cheers,
>  >
>  > Michael
>  >
>  > On Fri, Feb 8, 2008 at 4:10 PM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
>  > >
>  > > On Fri, 2008-02-08 at 22:59 +0800, Eugene Teo wrote:
>  > > > RLIMIT_RTTIME was introduced to allow the user to set a runtime timeout on
>  > > > real-time tasks: http://lkml.org/lkml/2007/12/18/218. This patch updates
>  > > > /proc/<pid>/limits with the new rlimit.
>  > >
>  > > Ah, didn't know about that file, thanks!
>  > >
>  > > > Signed-off-by: Eugene Teo <eugeneteo@...nel.sg>
>  > >
>  > > Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>  > >
>  > >
>  > > > ---
>  > > >  fs/proc/base.c |    1 +
>  > > >  1 files changed, 1 insertions(+), 0 deletions(-)
>  > > >
>  > > > diff --git a/fs/proc/base.c b/fs/proc/base.c
>  > > > index c59852b..dcf7be8 100644
>  > > > --- a/fs/proc/base.c
>  > > > +++ b/fs/proc/base.c
>  > > > @@ -412,6 +412,7 @@ static const struct limit_names lnames[RLIM_NLIMITS] = {
>  > > >       [RLIMIT_MSGQUEUE] = {"Max msgqueue size", "bytes"},
>  > > >       [RLIMIT_NICE] = {"Max nice priority", NULL},
>  > > >       [RLIMIT_RTPRIO] = {"Max realtime priority", NULL},
>  > > > +     [RLIMIT_RTTIME] = {"Max realtime timeout", "us"},
>  > > >  };
>  > > >
>  > > >  /* Display limits for a process */
>  > >
>  > > --
>  > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>  > > the body of a message to majordomo@...r.kernel.org
>  > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
>  > > Please read the FAQ at  http://www.tux.org/lkml/
>  > >
>  >
>  >
>  >
>
>



-- 
Michael Kerrisk
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