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Date: Thu, 4 Apr 2013 09:20:38 +0200
From: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20130404072038.GA24402@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel]
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 =?utf-8?q?mance_of_dataplane?=
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To: Zhangleiqiang <zhangleiqiang@huawei.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, "Luohao (brian)" <brian.luohao@huawei.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Haofeng <haofeng@huawei.com>, leiqzhang <leiqzhang@gmail.com>

On Tue, Apr 02, 2013 at 02:02:54AM +0000, Zhangleiqiang wrote:
> 	I have also finished the perf testing under Fedora 17 using IOZone, and the results also shown that the performance of disk with dataplane enabled did not have advantage over non-dataplane.

virtio-blk data plane is a win for parallel I/O workloads (that means
iodepth > 1).  The advantage becomes clearer with SMP guests.

In other words the big advantage is that data plane processes requests
without blocking the QEMU main loop or vCPU threads.

If your guest has 1 vCPU and/or your benchmarks only do a single stream
of I/O requests, then the difference may not be measurable.

Stefan