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RE: [Xen-devel] [Patch] Buffer disk I/O requests

To: "Ian Pratt" <Ian.Pratt@xxxxxxxxxxxx>, "Keir Fraser" <keir@xxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [Patch] Buffer disk I/O requests
From: "Han, Weidong" <weidong.han@xxxxxxxxx>
Date: Fri, 18 May 2007 11:14:14 +0800
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Thread-topic: [Xen-devel] [Patch] Buffer disk I/O requests
Ian Pratt wrote:
>> Buffered disk I/O improves disk I/O port access performance. It's
>> similar to buffered vga which is mmio. We ran SysBench random file
>> I/O test and found it reached about 10% improvement.
> How does it compare to just using the SCSI HBA support that got
> checked in a few days ago (in the qemu-dm 0.9.0 upgrade)?

In our test,  the performance of SCSI HBA is better than our patch
performance in qemu 0.9.0, But we find the total I/O preformance
downgrade a lot after upgrade to qemu 0.9.0. We suspect there may be
some issues in qemu 0.9.0.

> If we're going to add support for enabling buffering of ioport
> accesses beyond what we currently special case for the VGA it should
> be via a generic interface used by qemu to register sets of ports
> with xen and configure how they will be handled.
> Ian

Yes, if there are many these buffering cases, using a generic interface
is a final solution.

-- Weidong

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