Re: [Xen-devel] extremely slow disk access

[Steven H. <Ste...@cl...>]

> Hi list members,
> 
> I have a fresh FC3 with fresh bk clone of xen-2.0.bk.  It builds and 
> installs without complaint.
> 
> "/lib/tls" has been moved to "/lib/tls.disabled".
> 
> My understanding is that in a stand-alone (no vms running) situation the 
> performance difference between a standard kernel and a xen enabled 
> kernel should be roughly the same.  Is this correct?
> 
> 2.6.10-xen0 boots with no errors, but the mouse seems jerky and slow to 
> respond but is functional.
> 
> Networking is up and functional.
> 
> The drives are IDE in a raid0 using lvm.  The m/b is typical budget x86 
> with 1GB ram and 1GHz Athlon.  It has been in various uses without 
> failure for a couple years.
> 
> As a test I created a logical volume "Main/test" of 1G rw and formatted 
> it with ext3.  The inode creation part took perhaps 1 second but the 
> journal creation took over 1 minute.  I was able to have lunch (and do 
> the dishes) in the time it took to format 18G.
> 
> Reboot into 2.6.9 non-xen and try the same experiment and the entire 
> process takes less than 2 seconds.
> 
> I looked in /proc/interrupts but nothing there seems awry, i.e. no 
> runaway counts.
> 
> Does anyone have any idea what may be wrong or where I should look next?

Looks like you're falling back to PIO mode under Xen. 

Have you compiled in support for your IDE chipset? 

cheers,

S.