Re: [Xen-devel] poor I/O performance on domU

[Anthony Liguori <aliguori@xxxxxxxxxx>]

On Thu, 2005-01-13 at 10:06, Jan Kundrát wrote:
> ttylinux's rootfs is exported from ext3 fs via loopback device, could it 
> be the cause of troubles?

I think that's a reasonable answer.  It should be easy to test though. 
Try your same test on dom0 and use /dev/loopN where N is the loopback
device that has your rootfs on it.

The difference between testing /dev/loopN access on dom0 and the virtual
block device on domU should tell you the Xen-imposed performance
penalty.

I did a quick test on my system and there was a 50% slowdown using the
loopback device doing your test so I imagine it's that.

Regards,

> -jkt
-- 
Anthony Liguori
Samba, Linux/Windows Interoperability
Linux Technology Center (LTC) - IBM Austin
E-mail: aliguori@xxxxxxxxxx
Phone: (512) 838-1208
Tie Line: 678-1208



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