On Tue, 20 Nov 2007, Kris Kennaway wrote: > Yar Tikhiy wrote: >> Hi all, >> >> SCHED_ULE seems to do an unfair job to processes with low niceness >> or with real-time priority. Here are my observations: >> >> A few days ago I noticed that music (played by Totem, Gnome's default >> player) would pause for a fraction of second each time I did something >> in X/Gnome, such as switched between windows, clicked on a link in >> the web browser, etc. Then I found that music was jerky only if >> the player ran with a negative niceness or a real-time priority: >> As soon as I returned it to niceness 0 and normal priority, sound >> became totally seamless notwithstanding my activity in X. >> >> The approximate value required for the effect to appear was niceness >> as low as -5 or RT priority as high as 10; niceness -1 or rtprio 1 >> wasn't enough. >> >> Curious, I substituted SCHED_4BSD for SCHED_ULE in my otherwise >> GENERIC kernel, and the jerkiness of sound was gone irrespective >> of the niceness or RT priority of the player. >> >> To rule out other possible causes, I also tried kernels with SCHED_ULE >> but without SMP or without debug stuff (INVARIANTS+WITNESS), but >> the issue was there in both cases, unlike in the case of SCHED_4BSD. >> >> Of course, X+Gnome+stuff isn't the clearest environment for debugging >> schedulers, but multimedia apps are rather sensitive to scheduling >> quality. This case should be rather obvious: When I click in an >> inactive window, some processes are woken that have been idle. >> After that the high-priority player isn't scheduled long enough for >> the hardware audo buffer to drain, although it would be scheduled >> soon if it had normal priority. >> >> Did I hit a known issue? > > Others have reported it, but I don't know if Jeff has had time to investigate > yet. > I tried to reproduce this recently by running mplayer with various nice values while scrolling around a lot in firefox. This is on a 1.4ghz machine. I didn't encounter any problems. If anyone is having nice related problems with ULE I'd love a simple test case that shows it. I tried installing boinc which was mentioned in other threads but had trouble contacting the servers and getting it setup. Something simpler would be very beneficial. Thanks, Jeff > Kris >Received on Wed Jan 02 2008 - 03:56:17 UTC
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