Hi,
I could reproduce it and I bisected it down to this commit.
12d4536f7d911b6d87a766ad7300482ea663cea2 is the first bad commit
commit 12d4536f7d911b6d87a766ad7300482ea663cea2
Author: Anthony Liguori <aliguori@xxxxxxxxxx>
Date: Mon Aug 22 08:24:58 2011 -0500
-martin
On 22.02.2012 20:53, Stefan Hajnoczi wrote:
On Wed, Feb 22, 2012 at 4:48 PM, Dongsu Park
<dongsu.park@xxxxxxxxxxxxxxxx> wrote:
Try turning ioeventfd off for the virtio-blk device:
-device virtio-blk-pci,ioeventfd=off,...
You might see better performance since ramdisk I/O should be very
low-latency. The overhead of using ioeventfd might not make it
worthwhile. The ioeventfd feature was added post-0.14 IIRC. Normally
it helps avoid stealing vcpu time and also causing lock contention
inside the guest - but if host I/O latency is extremely low it might
be faster to issue I/O from the vcpu thread.
Thanks for the tip. I tried that too, but no success.
My guesses have all been wrong. Maybe it's time to git bisect this instead :).
Stefan
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