On Wed, May 09, 2001 at 04:33:36PM -0600, Chris Jones wrote:
> On Wed, May 09, 2001 at 09:22:08PM +0200, Manuel Bouyer wrote:
> 
> > Do the scsi controllers share interrupts with other devices ?
> 
> Yes.
> 
> uhci0: interrupting at irq 10
> siop1: interrupting at irq 10
> 
> But that's it, and uhci0 isn't doing much; I have no USB devices
> plugged in.  ISTR that the uhci code polls a few times a second for
> new devices, but it doesn't generate interrupts unless there are
> devices plugged in.  I could be wrong, though.

Hum, and if this was the problem this would affect both read and write
performances.

> 
> > While testing disks speed, could you run a 'systat vm' and look at
> > irq rates ?
> 
> ~600 on write, ~4800 on read, for irq 10.
> 
> > Do you get decent read speed out of these disks ?
> 
> Yes.  :)  About 9 to 9.5 MB/s.
> 
> Is it normal to expect write performance to be that much worse than
> read performance?  Why would I have one disk that writes as fast as it
> reads?

Maybe write cache is turned off on some of your disks ?
I don't know how to check this, though ...

--
Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@lip6.fr
--