[linux-audio-user] Linux DAW otimization (and Kanotix)

[Wolfgang Hoffmann]

On Saturday 18 February 2006 18:54, Lee Revell wrote:
> On Sat, 2006-02-18 at 00:47 -0800, Kevin Cosgrove wrote:
> > On 18 February 2006 at 0:15, Lee Revell <rlrevell at joe-job.com> wrote:
> > > This helps a lot:
> > > echo 64 > /sys/block/hdc/queue/max_sectors_kb
> > > (replace hdc with your drive, repeat for all of them)
> >
> > Interesting.  What does that do?
>
> It limits the amount of disk IO that can be "in flight" at once, which
> limits the amount of work the IDE driver will do in a single interrupt,
> which improves the worst case disk IO induced latency.
>
> It's not going to help with an -rt kernel, only mainline.
>
> I'd be interested to see what results people get...
>
> Lee

I suppose it also work with SATA drives, doesn't it? At 
least /sys/block/sda/queue/max_sectors_kb is available here.

I just tried with Ubuntu's dapper's stock 2.6.15 kernel. Jackd runs at 44100Hz 
samplerate and buffersize 256 samples (5.8ms periods). Hardware is an AOpen 
i915GMm-HFS board with a Pentium M 730 (1.6 GHz) and a RME Digi96/8 PAD.

Default max_sectors_kb is 1024, giving me casual xruns of up to 16 ms on an 
idle machine. With max_sectors_kb at 64, xruns reduce to max. 5 ms. Setting 
max_sectors_kb smaller than 64 seems to give no further improvement.

So it definitely helps, but not enough to go without -rt for me.

Wolfgang