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From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] converting the block layer from coroutines to threads |
Date: | Fri, 24 Feb 2012 13:22:34 -0600 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.23) Gecko/20110922 Lightning/1.0b2 Thunderbird/3.1.15 |
On 02/24/2012 01:02 PM, Paolo Bonzini wrote:
Hi all, a few weeks ago Stefan Hajnoczi pointed me to his work on virtio-blk performance. Stefan's work had two sides. First, he captured very nice performance data of the block layer at http://www.linux-kvm.org/page/Virtio/Block/Latency; second, in order to measure peak performance, he basically implemented "vhost-blk" in userspace.
I don't think the improvements here have anything to do with the block layer.We've done the same thing with virtio-net and saw impressive performance results as a consequence. Conversely, we see a similar improvement by applying the same technique to vhost-net.
Virtio really wants each virtqueue to be processed in a separate thread. On a multicore system, there's considerable improvement doing this.
I think that's where we ought to start. We really just need the block layer to be re-entrant, we don't actually need qcow2 or anything else that uses coroutines to use full threads.
Or at least, as far as I know, we don't have any performance data to suggest that we do.
Regards, Anthony Liguori
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