[linux-audio-user] The trouble with disks

John Anderson ardour at semiosix.com
Fri Dec 19 11:45:02 EST 2003

On Fri, 2003-12-19 at 15:34, Mark Knecht wrote:
> > What are the other options? I've looked at PCI latencies for card and
> > drive controller, IRQ ordering (although APIC seems to make this
> > irrelevant, or at least uncontrollable), OS disk scheduler
> > (anticipatory, deadline and cfq), tagged queueing (high values almost
> > guarantee xruns on recording but don't seem to improve playback).
> > 
> > Sheesh, at this rate if I get another dual-processor machine, I'll be
> > able to run jackd at -p 16 -n 2 :-|
> A dual-processor system won't necessarily change a disk latency problem.

I had a dual-processor system until it died about 3 weeks ago. It
definitely didn't have this problem, even though it's using physically
the same SCSI controller and disk. Well, it had a 64bit PCI slot for the
controller. OK, I've upgraded to 2.6 since then, in a partially
successful attempt to reduce the extent of the dropouts.

> Have you tried running with larger buffers? Sorry but I don't have the
> original post. Try -p 2048 -n 2 or -p 1024 -n 2 or -p 512 -n 4/8/16 if
> your card accepts it and see what happens. Possibly there is just a
> better setting to be using.

Still happens, but less, at -p 2048 -n 2 which is the largest the card
will accept.

> Also, have you run Benno's latency test app? It's good at showing
> problems like other apps stepping in and causing problems somewhere, and
> it can guide you towards the best -p/-n settings.

Yip, 0 overruns on all tests at 2x128.

Real headscratcher, innit?


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