Re: [Qemu-devel] [PATCH RFC 1/2] rng-egd: improve egd backend performance

[Amit Shah]

On (Mon) 16 Dec 2013 [15:19:31], Anthony Liguori wrote:
> On Mon, Dec 16, 2013 at 8:36 AM, Amit Shah <address@hidden> wrote:
> > On (Mon) 09 Dec 2013 [22:10:12], Amos Kong wrote:
> >> Bugzilla: https://bugs.launchpad.net/qemu/+bug/1253563
> >>
> >> We have a requests queue to cache the random data, but the second
> >> will come in when the first request is returned, so we always
> >> only have one items in the queue. It effects the performance.
> >>
> >> This patch changes the IOthread to fill a fixed buffer with
> >> random data from egd socket, request_entropy() will return
> >> data to virtio queue if buffer has available data.
> >>
> >> (test with a fast source, disguised egd socket)
> >>  # cat /dev/urandom | nc -l localhost 8003
> >>  # qemu .. -chardev socket,host=localhost,port=8003,id=chr0 \
> >>         -object rng-egd,chardev=chr0,id=rng0,buf_size=1024 \
> >>         -device virtio-rng-pci,rng=rng0
> >
> > First thing I can think of is the egd protocol has a length field in
> > the header, and if that isn't properly filled, the results are bound
> > to be erratic.
> 
> The test is bogus.
> 
> egd is a protocol.  You can't just pipe /dev/urandom into it.

Can you suggest a way to test this the right way?

                Amit