Messages in this thread | | | Date | Thu, 1 Apr 2010 10:43:11 +0200 | From | Michael Grzeschik <> | Subject | Re: Issues with Patch: "sched: Improve latencies and throughput" |
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On Thu, Apr 01, 2010 at 07:49:46AM +0200, Mike Galbraith wrote: > On Thu, 2010-04-01 at 00:31 +0200, Michael Grzeschik wrote: > > We are using an arm mx31 embedded cpu with the v2.6.34 Kernelrelease and > > realized some issues with the scheduling behaviour the patch "sched: > > Improve latencies and throughput" [1] by Mike Galbraith introduced to > > the kernel. > > > > When we used the alsa utility aplay to pipe some audio through an > > usbaudio device and put some scheduling overhead on the device, the > > amount of underruns, due to the not fast enough refilled ring buffer, > > was noticable increased with that patch [1] applied. Until we reverse > > applied the patch the amount of underruns was appreciable lower. > > Testcase?
What we did was:
# Copy some audiofile to /dev/shm $ cp audiofile.wav /dev/shm
# Play that file with aplay in background $ aplay /dev/shm/auduifile.wav &
# Put some scheduling load on the system $ hackbench 6
We did use this on an MX31 from Freescale running with about 500 MHz and the generic usbaudio driver to play the audio throgh an C-Media USB audiodongle.
Expected results with that patch:
underrun!!! (at least 323.946 ms long) < -- aplay underrun!!! (at least 59.477 ms long) < -- " underrun!!! (at least 194.873 ms long) < -- " Time: 7.048 < -- hackbench Time: 6.841 < -- " underrun!!! (at least 115.456 ms long) < -- aplay underrun!!! (at least 37.849 ms long) < -- " underrun!!! (at least 588.637 ms long) < -- " Time: 7.23 < -- hackbench
results without the patch:
Time: 3.728 < -- hackbench underrun!!! (at least 58.557 ms long) < -- aplay Time: 3.771 < -- hackbench underrun!!! (at least 97.538 ms long) < -- aplay Time: 3.732 < -- hackbench Time: 3.630 < -- .... Time: 3.636 Time: 3.643
Thanks, mgr
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