The kernel has no low-latency patches applied.
That will make a difference.
The sound system is M-Audio DIO2448 + OSS drivers
Hard disk is standard IDE, tuned with hdparm
Distro is Debian 3.0 with quite a lot of "testing" packages installed.
Base H/W 800MHz Duron + 256M RAM.
This does seem to be related to the disk I/O scheduling change, or
possibly virtual memory
Possible options seem to be:
1. Apply low latency patches
Yes (low-latency and preemptible)
2. Upgrade to 2.4.22
Well, why not? I do recall I had some problems with lowlatency somewhere
between between 2.4.14 en 2.4.22, related with a specific DMA
controller.. You might want to go for 2.4.23 though!
3. Upgrade to 2.6.0
That's a though question.. I think it is good of more linux-audio-users
move to 2.6, so we can get a clear idea of how linux-audio (and
specifically low latency) is going along with 2.6, and where the
problems are. On the other hand, it might be better to wait a while. As
discussed in the thread about 2.6, latency is still beter with a patched
2.4, and there is a lot of stuff from Andrew Morton waiting to go into
4. something else?
Well, just that, since you are using Debian, you might want to build a
debian kernel package. It's a bit tricky if it's the first time you do
it, but applying patches is done nicely for you. If you want to walk
this road, let me know, and I can tell you how to do it. On the other
hand, if it's only one machine... Using the vanilla kernel and patching
it is probably easier.