Messages in this thread | | | Date | Fri, 11 Apr 2008 10:56:49 +0200 | From | "Michael Kerrisk" <> | Subject | Re: [PATCH] proc: Add RLIMIT_RTTIME to /proc/<pid>/limits |
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On Thu, Feb 28, 2008 at 5:21 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. > > 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).
So I have another question: why is the granularity of this rlimit microseconds? On the one hand, specifying limits down at the microsecond level seems (to my naive eye) unlikely to be useful. (But perhaps I have missed a thread where this was explained.) On the other hand, it means that on 32-bit the largest time limit we can set is ~4000 seconds, and I wonder if there are scenarios where it might be useful to have larger limits than that.
Why not, for example, have a granularity of milliseconds?
Cheers,
Michael
> > On Fri, Feb 8, 2008 at 4:10 PM, Peter Zijlstra <a.p.zijlstra@chello.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@kernel.sg> > > > > > > Acked-by: Peter Zijlstra <a.p.zijlstra@chello.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@vger.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 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
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