On 06/29/2015 03:22 PM, George Dunlap wrote:
On Wed, Jun 24, 2015 at 1:06 PM, Juergen Gross <jgr...@suse.com> 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?
Yes.
I don't actually understand your question -- is the overhead
acceptable for what?
Acceptable for the decision to build the backend in qemu only. When I
posted the first draft of my kernel backend to lkml the question was
raised why I couldn't do this in userland via libusb.
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.
In case the performance is regarded to be sufficient I won't retry to
push a kernel backend. So there will be none in the near future.
If the performance is not good enough I'll give the kernel backend
another try. If it's being accepted I probably won't do the qemu one.
Juergen
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