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Re: [Xen-devel] [BUNDLE] Xen Share w/ block device

To: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [BUNDLE] Xen Share w/ block device
From: Andrew Warfield <andrew.warfield@xxxxxxxxxxxx>
Date: Thu, 16 Feb 2006 21:14:31 -0800
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> Here's the compulsory benchmark numbers (same machine, uniproc 3GHz
> Pentium 4), ext2 filesystem in a file in dom0 served to dom1:
> Current block device:
>         dd if=/dev/zero of=test bs=1M count=1000: 71.5527 seconds

By my accounting that looks to be about 14 MB/s off your block device
using the existing split drivers... If you can't saturate the disk on
a 3 Ghz box I'd have to think that something has gone desperately
wrong.  Has a block performance bug slid in to unstable or something?

I don't doubt that better memory performance can be achieved by
adjusting event notification frequency/batching -- as you pointed out
earlier... but block devices are a pretty weird place to try to win. 
I'd expect the numbers from the two tests you're running to be
identical -- and bottlenecked on the disk.  By a lot.


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