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Date: Mon, 16 Dec 2013 22:06:36 +0530
From: Amit Shah <amit.shah@redhat.com>
Message-ID: <20131216123540.GB6582@grmbl.mre>
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Subject: Re: [Qemu-devel] [PATCH RFC 1/2] rng-egd: improve egd backend
	performance
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To: Amos Kong <akong@redhat.com>
Cc: varadgautam@gmail.com, qemu-devel@nongnu.org, anthony@codemonkey.ws

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.

I haven't been able to find a spec detailing the way egd API, perhaps
Anthony knows how to best pass data to qemu via egd.

		Amit