Re: [LAD] MidiSport vs. UA25

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

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