linuxaudio.org

On Saturday 18 February 2006 18:54, Lee Revell wrote:

quoted text
> On Sat, 2006-02-18 at 00:47 -0800, Kevin Cosgrove wrote:

> > On 18 February 2006 at 0:15, Lee Revell  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