Subject: Re: [linux-audio-dev] Lots about latency and disk i/o and JACK...
On Wed, 3 Oct 2001 22:50:45 +1000
> On Wed, Oct 03, 2001 at 08:09:53AM -0400, Paul Davis wrote:
Hi
This archive was generated by hypermail 2b28
: Mon Oct 08 2001 - 10:41:28 EEST
From: CLOTILDE (guy.clotilde_AT_wanadoo.fr)
Date: Mon Oct 08 2001 - 10:37:22 EEST
Andre Pang <ozone_AT_algorithm.com.au> wrote:
>
> > >On Karl's paper of latency measurements there was mentioned that the low-
> > >latency patches have actually little effect and the reasone for bad latency on
> > >some systems is actually IDE. Could you actually tell as more about this,
> >
> > this is not strictly true. the IDE drivers (and devices) are the worst
> > offenders, but they are far the only place in the mainstream kernel
> > where the kernel could block a runnable task for a (very) long time.
>
> This is true, but turning on DMA support for the IDE hard disk
> lowers your latencies and CPU usage by several orders of
> magnitude. Try running the "hdparm -d1 -X66 /dev/hda" command.
> Replace /dev/hda with your hard drive, as appropriate. -X66
> is DMA mode2; the newest HDs and chipset may be DMA mode3, 4, or,
> 5, which are -X67, -X68, and -X69, respectively. Try them in
> reverse order; you'll just get back a "DMA mode not supported"
> message if your HD/chipset can't handle that speed.
>
> If anybody's really interested, I can do benchmarks to see what
> the difference is ...
Yes I am interested. Thanks.