On Thu, 2011-10-06 at 21:14 -0700, Dylan Reid wrote: > > Obviously we're somewhat biased here, but I think it would > be prudent of > > you to revisit some of the previous results. Pierre has done > a lot of > > work on the Intel side and numerous other companies are > using PA in an > > embedded space without any of the CPU problems you mention. > There was > > indeed a "period of pain" where such issue were caused, most > typically > > from the timer based scheduling mechanism that PA implements > which many > > underlying ALSA drivers did not play nicely with. Since then > lots of the > > driver issues were fixed. > > > Yes, the general experience has been that Pulse does well in > embedded > environments - power problems with it are pretty much always > down to > issues in the drivers propagating up the stack rather than > Pulse itself. > There's production hardware out there using Pulse which would > really > notice. > > I took some quick measurements of alsa and pulseaudio playback on an > Acer Chromebook. I tested with a latency of 200ms and 10ms. I used a > pulse audio at commit b0d9c78 plus a patch I got from Pierre-Louis to > avoid SRC if possible(attached). These are the results I got. Two > problems, it's using a ton a CPU in the low latency case, and it when > asked for 10ms latency it was giving me around 50ms. > > > This table shows the cpu usage measured with 'top -d10 -n2 -b'. I > attached the python script I used to run the test in case anyone wants > to reproduce. Just as a sanity check, I hope you're running these tests with the CPU frequency pegged at a single value. top numbers are a percentage of the current CPU frequency. > I've attached the PA config files I am using, along with the log > output(pulselog). The most suspicious thing in there is the failure > to get RT scheduling. Is there something obviously wrong with the > configs that would cause these numbers to be so high, or to prevent > 10ms latency working? At some point, you might want to build PulseAudio with Orc[1] support enabled for performance gains[2] when software volumes are applied. Cheers, Arun [1]: http://code.entropywave.com/projects/orc/ [2]: http://lists.freedesktop.org/archives/pulseaudio-discuss/2010-October/007952.html
