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Re: [Qemu-devel] [question] the patch which affect performance of virtio
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [question] the patch which affect performance of virtio-scsi |
Date: |
Tue, 03 Feb 2015 09:42:03 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 |
On 03/02/2015 03:31, Wangting (Kathy) wrote:
> Hi Paolo,
>
> Recently I test IO performance with virtio-scsi, and find out that the patch
> of
> "virtio-scsi: add support for the any_layout feature" affects IO performance
> of model
> with 4KB 32iodepth sequence read.
>
> Why cdb and sense is removed from the struct of VirtIOSCSICmdReq and
> VirtIOSCSICmdResp?
Because I could not find any other way to implement ANY_LAYOUT, and
virtio 1.0 requires that feature.
The performance however was already improved in commit faf1e1f
(virtio-scsi: Optimize virtio_scsi_init_req, 2014-09-16).
Paolo
> How do you consider the impact of the changes to the performance?
> Although the latest version of qemu can optimize the performance by the way
> of reading merger,
> I think the affect of this patch cannot be ignored.
Re: [Qemu-devel] [question] the patch which affect performance of virtio-scsi,
Paolo Bonzini <=