On Sat, Sep 26, 2009 at 04:28:42AM +0200, Jens M Andreasen wrote:
> On Fri, 2009-09-25 at 21:50 +0200, Arnout Engelen wrote:
> > Attached are the results on an untuned Debian Testing machine (2.6.30-1-686)
> > started with 'chrt -f 50 ./src/alsa-midi-latency-test -s 40'
>
> What do you mean by "untuned"? Is this without RT-patches?
This was without RT-patches. I now installed the 2.6.31-rt11-686-multimedia
from 64studio. Without any changes, this actually seemed to perform somewhat
poorer compared to the stock Debian one.
I did some tweaks:
- increased the rtprio for the USB IRQ handler
- decreased the 'latency_timer' value for my wireless network card and cardbus
slot
- tried to increase 'latency_timer' for the USB controller, but it remained
at 0 - i guess it doesn't support this option
After this, the performance is comparable.
> > The Edirol sure outperformed the MidiSport - the difference didn't seem huge
> > though.
>
> What I find most disturbing is the distribution, ranging from better
> than perfect to on the edge of unusable. How much of this can be
> attributed to the USB-stack?
Anything I could try to isolate that?
Arnout
> calibrating high precision timer loop.. done.
time diff = 0.00
loops/sec = 8096691308977433.00
> sampling 10000 midi latency values - please wait..
> press Ctrl+C to abort test.
> skipping first 40 latency samples.
sample; latency_ms; latency_ms_worst
41; 2.31; 2.31
42; 3.04; 3.04
57; 3.15; 3.15
58; 3.95; 3.95
148; 4.00; 4.00
311; 4.01; 4.01
434; 4.03; 4.03
624; 4.06; 4.06
710; 4.06; 4.06
10000; 2.40; 4.06
> done.
> latency distribution:
...
1.1 - 1.2 ms: 8 #
...
1.4 - 1.5 ms: 1 #
...
1.7 - 1.8 ms: 37 #
1.8 - 1.9 ms: 60 #
1.9 - 2.0 ms: 20 #
2.0 - 2.1 ms: 8 #
2.1 - 2.2 ms: 10 #
2.2 - 2.3 ms: 91 #
2.3 - 2.4 ms: 6444 ###################################################
2.4 - 2.5 ms: 1087 #########
2.5 - 2.6 ms: 515 #####
2.6 - 2.7 ms: 241 ##
2.7 - 2.8 ms: 115 #
2.8 - 2.9 ms: 94 #
2.9 - 3.0 ms: 110 #
3.0 - 3.1 ms: 74 #
3.1 - 3.2 ms: 43 #
3.2 - 3.3 ms: 32 #
3.3 - 3.4 ms: 38 #
3.4 - 3.5 ms: 38 #
3.5 - 3.6 ms: 37 #
3.6 - 3.7 ms: 26 #
3.7 - 3.8 ms: 24 #
3.8 - 3.9 ms: 15 #
3.9 - 4.0 ms: 719 ######
4.0 - 4.1 ms: 111 #
> latency distribution:
...
2.2 - 2.3 ms: 6 #
2.3 - 2.4 ms: 4 #
...
2.5 - 2.6 ms: 1 #
2.6 - 2.7 ms: 1 #
2.7 - 2.8 ms: 1 #
2.8 - 2.9 ms: 3345 ###################################
2.9 - 3.0 ms: 4900 ##################################################
3.0 - 3.1 ms: 357 ####
3.1 - 3.2 ms: 362 ####
3.2 - 3.3 ms: 232 ###
3.3 - 3.4 ms: 98 #
3.4 - 3.5 ms: 55 #
3.5 - 3.6 ms: 27 #
3.6 - 3.7 ms: 16 #
3.7 - 3.8 ms: 17 #
3.8 - 3.9 ms: 18 #
3.9 - 4.0 ms: 12 #
4.0 - 4.1 ms: 16 #
4.1 - 4.2 ms: 7 #
4.2 - 4.3 ms: 14 #
4.3 - 4.4 ms: 16 #
4.4 - 4.5 ms: 9 #
4.5 - 4.6 ms: 6 #
4.6 - 4.7 ms: 13 #
4.7 - 4.8 ms: 4 #
4.8 - 4.9 ms: 9 #
4.9 - 5.0 ms: 369 ####
5.0 - 5.1 ms: 83 #
> SUCCESS
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