* changing timeslice in linux @ 2012-08-19 18:58 Xin Tong 2012-08-20 5:54 ` Mike Galbraith 0 siblings, 1 reply; 6+ messages in thread From: Xin Tong @ 2012-08-19 18:58 UTC (permalink / raw) To: linux-kernel I have 2 questions about linux 2.6 x86_64 scheduler. 1. is the default scheduling algorithm SCHED_NORMAL in linux ? 2. how do i change the time slice in linux source code ? Xin ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: changing timeslice in linux 2012-08-19 18:58 changing timeslice in linux Xin Tong @ 2012-08-20 5:54 ` Mike Galbraith 2012-08-20 14:51 ` Xin Tong 0 siblings, 1 reply; 6+ messages in thread From: Mike Galbraith @ 2012-08-20 5:54 UTC (permalink / raw) To: Xin Tong; +Cc: linux-kernel 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. > 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: changing timeslice in linux 2012-08-20 5:54 ` Mike Galbraith @ 2012-08-20 14:51 ` Xin Tong 2012-08-21 0:16 ` Namhyung Kim 0 siblings, 1 reply; 6+ messages in thread From: Xin Tong @ 2012-08-20 14:51 UTC (permalink / raw) To: Mike Galbraith; +Cc: linux-kernel On Sun, Aug 19, 2012 at 10:54 PM, Mike Galbraith <efault@gmx.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 ? Xin ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: changing timeslice in linux 2012-08-20 14:51 ` Xin Tong @ 2012-08-21 0:16 ` Namhyung Kim 2012-08-28 20:15 ` Xin Tong 0 siblings, 1 reply; 6+ messages in thread From: Namhyung Kim @ 2012-08-21 0:16 UTC (permalink / raw) To: Xin Tong; +Cc: Mike Galbraith, linux-kernel On Mon, 20 Aug 2012 07:51:52 -0700, Xin Tong wrote: > On Sun, Aug 19, 2012 at 10:54 PM, Mike Galbraith <efault@gmx.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 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: changing timeslice in linux 2012-08-21 0:16 ` Namhyung Kim @ 2012-08-28 20:15 ` Xin Tong 2012-08-28 20:16 ` Xin Tong 0 siblings, 1 reply; 6+ messages in thread From: Xin Tong @ 2012-08-28 20:15 UTC (permalink / raw) To: Namhyung Kim; +Cc: Mike Galbraith, linux-kernel 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@kernel.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@gmx.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 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: changing timeslice in linux 2012-08-28 20:15 ` Xin Tong @ 2012-08-28 20:16 ` Xin Tong 0 siblings, 0 replies; 6+ messages in thread From: Xin Tong @ 2012-08-28 20:16 UTC (permalink / raw) To: Namhyung Kim; +Cc: Mike Galbraith, linux-kernel 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@gmail.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@kernel.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@gmx.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 ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2012-08-28 20:16 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2012-08-19 18:58 changing timeslice in linux Xin Tong 2012-08-20 5:54 ` Mike Galbraith 2012-08-20 14:51 ` Xin Tong 2012-08-21 0:16 ` Namhyung Kim 2012-08-28 20:15 ` Xin Tong 2012-08-28 20:16 ` Xin Tong
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