Re: Issues with Patch: "sched: Improve latencies and throughput"
From: Michael Grzeschik
Date: Thu Apr 01 2010 - 04:43:25 EST
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"  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  applied. Until we reverse
> > applied the patch the amount of underruns was appreciable lower.
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
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 < -- ....
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