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Date: Tue, 28 Aug 2012 13:16:47 -0700 From: Xin Tong <xerox.time.tech@...il.com> To: Namhyung Kim <namhyung@...nel.org> Cc: Mike Galbraith <efault@....de>, linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: changing timeslice in linux another question is that when i try to launch many (24) RT processes. some of them do not seem to get scheduled. i query their scheduling properties. they all have SCHED_RR with priority 99, but some of them simply are not taking any CPU. Xin On Tue, Aug 28, 2012 at 1:15 PM, Xin Tong <xerox.time.tech@...il.com> wrote: > i changed the TIMESLICE defined in the sched.c > > 109 /* > 110 * These are the 'tuning knobs' of the scheduler: > 111 * > 112 * default timeslice is 100 msecs (used only for SCHED_RR tasks). > 113 * Timeslices get refilled after they expire. > 114 */ > 115 #define DEF_TIMESLICE (20 * HZ / 1000) > > > I compiled and installed the modified kernel, but when i looked at the > , i get a different number > > root@elm:~# cat /proc/sys/kernel/sched_rt_period_us > 1000000 > > > Xin > > On Mon, Aug 20, 2012 at 5:16 PM, Namhyung Kim <namhyung@...nel.org> wrote: >> On Mon, 20 Aug 2012 07:51:52 -0700, Xin Tong wrote: >>> On Sun, Aug 19, 2012 at 10:54 PM, Mike Galbraith <efault@....de> wrote: >>>> On Sun, 2012-08-19 at 11:58 -0700, Xin Tong wrote: >>>>> I have 2 questions about linux 2.6 x86_64 scheduler. >>>>> >>>>> 1. is the default scheduling algorithm SCHED_NORMAL in linux ? >>>> >>>> Yes. >>> Is there any document describing what the sched_normal is ? it is more >>> difficult than SCHED_RR to infer its meaning just based on its name ? >>>> >>>>> 2. how do i change the time slice in linux source code ? >>>> >>>> You shouldn't need to. You can tune "slice" by adjusting >>>> sched_latency_ns and sched_min_granularity_ns, but note that "slice" is >>>> not a fixed quantum. Also note that CFS preemption decisions are based >>>> upon instantaneous state. A task may have received a full (variable) >>>> "slice" of CPU time, but preemption will be triggered only if a more >>>> deserving task is available, so a "slice" is not the "max uninterrupted >>>> CPU time" that you may expect it to be.. but it is somewhat similar. >>>> >>>> -Mike >>>> >>> This can be done without recompiling and reinstalling the kernel ? >>> maybe one simply needs to write to a device file under /dev ? >> >> You can find those files under /proc/sys/kernel/. >> >> Thanks, >> Namhyung -- 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/
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