Re: [Xen-devel] pvUSB backend performance

[George Dunlap <dunlapg@xxxxxxxxx>]

On Wed, Jun 24, 2015 at 1:06 PM, Juergen Gross <jgross@xxxxxxxx> wrote:
> Hi,
>
> my qemu integrated pvUSB backend is now running stable enough to do
> some basic performance measurements. I've passed a memory-stick with
> about 90MB of data on it to a pv-domU. Then I read all the data on
> it with tar and looked how long this would take (elapsed time):
>
> in dom0:                     5.2s
> in domU with kernel backend: 6.1s
> in domU with qemu backend:   8.2s
>
> So the qemu backend is about 30% slower than the kernel backend. Is
> this acceptable?

Just to be clear, you mean having qemu act as a pvusb backend (a la
qdisk), not emulated, is that correct?

I don't actually understand your question -- is the overhead
acceptable for what?

I think in an ideal world the toolstack will use the kernel backend if
it's available, and fall back to a qemu backend if it's not available.

 -George

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