Cc'd to LKML & Ingo.
L.
Klaus Schulz wrote:
Hi there.
Am Dienstag, den 31.07.2007, 10:26 +0200 schrieb Klaus Schulz:
Hi folks.
I am currently testing the 2.6.22.1 cfs-rt9 vs. ck1 on my rather pure
realtime high-end-audio setup. (NO X, just a terminal, streaming .wav.
I am using my own written player and brutefir as the audio engine.)
Comment: This is not a standard (amarok or xmms setup), all buffers in
the chain are very small. Any problem will immidetialy end up in xruns.
The sounddriver, HW (pci-bus etc.) are tweaked accordingly
Until now ck1 on 2.6.22 is giving me better results (less audible
distortions) and runs extremely stable compared to cfs.
Under ck I ran my player with schedtool -R -p 98, which was better than
running it e.g. with nice -20
Both setups under cfs were giving me worse results than ck.
With CFS I also experienced XRUNS from time to time, what never happened
with ck.
However:
When looking at the latest performance statistics cfs vs. ck which are
spread around here, I am wondering, what might cause the differences.
With ck I tweaked the rr_interval to 6 and was running at 10000Hz,
which caused obvious improvements.
These options I do not have with CFS.
I am wondering if sched_granularity_ns should be touched when using cfs.
I googled somewhere that bringing it down to e.g. 250000 instead of
4000000 would smoothen the audio playback. I havn't tried it yet. I am
wondering if this tweak is still applicable.
I did test now decreasing the sched_granularity_ns to 250000.
There is still a clearly audible difference comparing ck and cfs.
ck Ídelivers cristal clear sound. With cfs I still get quite some
distortions.
Any hints how to improve the situtation are welcome.
I'd be happy to get a hint on how to tweak the system parameters best to
give cfs a fair chance. I am also wondering how the timer freqency could
by increased under a cfs-patched kernel.
Info: dynamic ticks and IRQ balancing are off for the time being.
/proc/sys/dev/rtc is set to 4096 (gave me best results)
( I don't have a clue how all the (rtc)-timers in the OS interact,
To me it is just a trial and error exercise to figure out which
setup sounds best)
THX for your advise.
Cheers
\Klaus
Cheers
\Klaus
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