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



Anthony Liguori wrote:
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.


Only rootfs is exported from loopback device and I'm benchmarking access to dom0's /dev/hda exported to domU as read-only.

As the rootfs image is quite small (16MB), I can't easily test access speeds because it will fit into cache.

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.

Accessing exported loopback or some other device?


-jkt

--
cd /local/pub && more beer > /dev/mouth



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