On Wed, 3 Oct 2001 22:50:45 +1000 Andre Pang <[EMAIL PROTECTED]> wrote:
> On Wed, Oct 03, 2001 at 08:09:53AM -0400, Paul Davis 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 ... Hi Yes I am interested. Thanks.
