BFS vs. mainline scheduler benchmarks and measurements
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From: Peter Zijlstra on 9 Sep 2009 05:20 On Wed, 2009-09-09 at 12:05 +0300, Nikos Chantziaras wrote: > Thank you for mentioning min_granularity. After: > > echo 10000000 > /proc/sys/kernel/sched_latency_ns > echo 2000000 > /proc/sys/kernel/sched_min_granularity_ns You might also want to do: echo 2000000 > /proc/sys/kernel/sched_wakeup_granularity_ns That affects when a newly woken task will preempt an already running task. > I can clearly see an improvement: animations that are supposed to be > fluid "skip" much less now, and in one occasion (simply moving the video > window around) have been eliminated completely. However, there seems to > be a side effect from having CONFIG_SCHED_DEBUG enabled; things seem to > be generally a tad more "jerky" with that option enabled, even when not > even touching the latency and granularity defaults. There's more code in the scheduler with that enabled but unless you've got a terrible high ctx rate that really shouldn't affect things. Anyway, you can always poke at these numbers in the code, and like Mike did, kill sched_init_granularity(). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Nikos Chantziaras on 9 Sep 2009 05:50 On 09/09/2009 12:17 PM, Peter Zijlstra wrote: > On Wed, 2009-09-09 at 12:05 +0300, Nikos Chantziaras wrote: > >> Thank you for mentioning min_granularity. After: >> >> echo 10000000> /proc/sys/kernel/sched_latency_ns >> echo 2000000> /proc/sys/kernel/sched_min_granularity_ns > > You might also want to do: > > echo 2000000> /proc/sys/kernel/sched_wakeup_granularity_ns > > That affects when a newly woken task will preempt an already running > task. Lowering wakeup_granularity seems to make things worse in an interesting way: With low wakeup_granularity, the video itself will start skipping if I move the window around. However, the window manager's effect of moving a window around is smooth. With high wakeup_granularity, the video itself will not skip while moving the window around. But this time, the window manager's effect of the window move is skippy. (I should point out that only with the BFS-patched kernel can I have a smooth video *and* a smooth window-moving effect at the same time.) Mainline seems to prioritize one of the two according to whether wakeup_granularity is raised or lowered. However, I have not tested Mike's patch yet (but will do so ASAP.) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Benjamin Herrenschmidt on 9 Sep 2009 06:00 On Tue, 2009-09-08 at 22:22 +0200, Frans Pop wrote: > Arjan van de Ven wrote: > > the latest version of latencytop also has a GUI (thanks to Ben) > > That looks nice, but... > > I kind of miss the split screen feature where latencytop would show both > the overall figures + the ones for the currently most affected task. > Downside of that last was that I never managed to keep the display on a > specific task. Any idea of how to present it ? I'm happy to spend 5mn improving the GUI :-) > The graphical display also makes it impossible to simply copy and paste > the results. Ah that's right. I'm not 100% sure how to do that (first experiments with gtk). I suppose I could try to do some kind of "snapshot" feature which saves the results in textual form. > Having the freeze button is nice though. > > Would it be possible to have a command line switch that allows to start > the old textual mode? It's there iirc. --nogui :-) Cheers, Ben. > Looks like the man page needs updating too :-) > > Cheers, > FJP > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo(a)vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Nikos Chantziaras on 9 Sep 2009 06:20 On 09/09/2009 12:40 PM, Nikos Chantziaras wrote: > On 09/09/2009 12:17 PM, Peter Zijlstra wrote: >> On Wed, 2009-09-09 at 12:05 +0300, Nikos Chantziaras wrote: >> >>> Thank you for mentioning min_granularity. After: >>> >>> echo 10000000> /proc/sys/kernel/sched_latency_ns >>> echo 2000000> /proc/sys/kernel/sched_min_granularity_ns >> >> You might also want to do: >> >> echo 2000000> /proc/sys/kernel/sched_wakeup_granularity_ns >> >> That affects when a newly woken task will preempt an already running >> task. > > Lowering wakeup_granularity seems to make things worse in an interesting > way: > > With low wakeup_granularity, the video itself will start skipping if I > move the window around. However, the window manager's effect of moving a > window around is smooth. > > With high wakeup_granularity, the video itself will not skip while > moving the window around. But this time, the window manager's effect of > the window move is skippy. > > (I should point out that only with the BFS-patched kernel can I have a > smooth video *and* a smooth window-moving effect at the same time.) > Mainline seems to prioritize one of the two according to whether > wakeup_granularity is raised or lowered. However, I have not tested > Mike's patch yet (but will do so ASAP.) I've tested Mike's patch and it achieves the same effect as raising sched_min_granularity. To round it up: By testing various values for sched_latency_ns, sched_min_granularity_ns and sched_wakeup_granularity_ns, I can achieve three results: 1. Fluid animations for the foreground app, skippy ones for the rest (video plays nicely, rest of the desktop lags.) 2. Fluid animations for the background apps, a skippy one for the one in the foreground (dekstop behaves nicely, video lags.) 3. Equally skippy/jerky behavior for all of them. Unfortunately, a "4. Equally fluid behavior for all of them" cannot be achieved with mainline, unless I missed some other tweak. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: David Newall on 9 Sep 2009 07:20
Benjamin Herrenschmidt wrote: > On Tue, 2009-09-08 at 22:22 +0200, Frans Pop wrote: > >> Arjan van de Ven wrote: >> >>> the latest version of latencytop also has a GUI (thanks to Ben) >>> >> That looks nice, but... >> >> I kind of miss the split screen feature where latencytop would show both >> the overall figures + the ones for the currently most affected task. >> Downside of that last was that I never managed to keep the display on a >> specific task. >> > > Any idea of how to present it ? I'm happy to spend 5mn improving the > GUI :-) Use a second window. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |