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Re: [Qemu-devel] IO performance test on the tcm-vhost scsi
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-devel] IO performance test on the tcm-vhost scsi |
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Date: |
Thu, 14 Jun 2012 14:27:15 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 |
Il 14/06/2012 14:07, Stefan Hajnoczi ha scritto:
> Perfect, thanks. virtio-scsi userspace is much better than virtio-blk
> here. That's unexpected since they both use the QEMU block layer. If
> anything, I would have expected virtio-blk to be faster!
Yes, I would have expected something similar. A blktrace would be
useful here because Asias measured the opposite---virtio-scsi being much
slower than virtio-blk.
> The second question is why is tcm_vhost faster than virtio-scsi
> userspace.
I would expect a difference on more high-end benchmarks (i.e. lots of
I/O to lots of disks), similar to vhost-blk. In this simple case I
wonder how much it is due to the vagaries of the I/O scheduler, or even
statistical noise.
Paolo