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Re: [Xen-devel] Serious performance issues

To: Anthony Liguori <aliguori@xxxxxxxxxx>
Subject: Re: [Xen-devel] Serious performance issues
From: Tommi Virtanen <tv@xxxxxxxxxxxxx>
Date: Fri, 04 Mar 2005 20:55:02 +0200
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Anthony Liguori wrote:
I tested the disk, it still transfers ~50MB/s. I don't seem to be
suffering from PIO mode. Also, things running from RAM cache are as
slow as from disk.
What version of Xen is this?

2.0.4, as packaged for Debian by Adam Heath at

If you're running xen-unstable, try xen-2.0.x or vice versa. Are you absolutely positive that you've got enough memory allocated to dom0?

As dom0 is my main environment, it gets almost all of the RAM.

title           Xen 2.6.10
root            (hd0,1)
kernel          /boot/xen.gz dom0_mem=917504
module          /boot/xen-linux-2.6.10+xen0 root=/dev/hda2 ro
module          /boot/initrd.img-2.6.10+xen0

That you've got the proper IO chipset support built into the kernel?

The config is pretty much identical between native linux and xen dom0.

That you've really got tls disabled (if you just move tls after an app has already launched using it it will still be using it until you restart the app)?

I have rebooted many times since the move.

These numbers seem too bad to be Xen's fault alone. Do you have swap enabled? Is there a great deal of swap activity?

There's 2 gigs of swap with under 3 megabytes used, no blocks going in
or out.

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