Subject: Re: [linux-audio-dev] 2.4.0-test8 low-latency
From: Paul Winkler (slinkp23_AT_yahoo.com)
Date: Wed Sep 13 2000 - 13:05:40 EEST
Chris Baugher wrote:
>
> I've just run Benno's latencytest on 2.4.0test8 with Andrew's newest
> low-latency patch. This is the machine:
(snip)
> I would say it's looking better!
I have high hopes! I'm compiling 2.4.0-test8 right now... will
report back on how that checks out.
I just finished my first latencytest of 2.4.0-pre6 and I'm getting
overruns during the disk read and copy tests - a half-dozen or so
latency peaks as high as 12 ms, with one or two peaks nearing 40 ms.
(Yes, I do have DMA-enabled IDE disks... just for laughs I did a
comparison run with DMA turned off and it was, predictably, quite
awful.)
I did also try running csound --sched (unofficial linux version of
course) and with no disk output, it does perform drastically better
than on an unpatched kernel. I got output buffers as low as 16 bytes
with no dropouts at all! Cool!
I've also been fiddling around with the latencytest scripts a bit,
mostly to add an optional sixth argument to choose the directory for
the temporary files.
Makes it easier to compare disk performance with different disks. I
also moved cpu_load into latencytest.h (make it easier to change)
and changed genhtml to print the chosen value of cpu_load on the
generated page.
cpu_load turns out to be quite important to me because on my celeron
333, 80% usage takes a verrrrry long time to finish (I thought it
locked the box but it was done when I got back from dinner) and
outputs bogus results. I gradually tweaked it downward to 76% which
appears to be the max my system can deal with.
Patch follows. I leave it up to Benno to decide whether any of these
modifications are a good idea...
--
................. paul winkler ..................
slinkP arts: music, sound, illustration, design, etc.
web page: http://www.slinkp.com
A member of ARMS: http://www.reacharms.com
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