Messages in this thread | | | Subject | Re: [PATCH] proc: Add RLIMIT_RTTIME to /proc/<pid>/limits | From | Peter Zijlstra <> | Date | Fri, 11 Apr 2008 11:01:25 +0200 |
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On Fri, 2008-04-11 at 10:56 +0200, Michael Kerrisk wrote: > 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?
The us scale seemed the best fit in that it allows sub-ms granularity while still allowing for quite long periods too. I'd preferred ns scale as that is what we use throughout the scheduler where possible - but that seemed too restrictive at the high end.
No real hard arguments either way.
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