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Date: Thu, 9 Apr 2009 18:13:41 +0100
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] Re: [libvirt] Re: [PATCH 2/3] Introduce monitor
	'wait' command
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To: "Daniel P. Berrange" <berrange@redhat.com>
Cc: libvir-list@redhat.com, Jan Kiszka <jan.kiszka@web.de>, qemu-devel@nongnu.org, Hollis Blanchard <hollisb@us.ibm.com>

Daniel P. Berrange wrote:
> One scheme would be to have a small buffer - enough to store say 10 events.
> If the monitor is blocking for write, and the buffer is full then start to
> discard all further events. When the buffer has more space again, then
> send an explicit 'overflow' event informing the app that stuff has been 
> dropped from the event queue.
>
> In normal circumstances the app would never see this message, but if there
> was some unexpected problem causing the app to not process events quickly
> enough, then at least it would be able to then detect that qemu has
> discarded alot of events, and re-synchronize its state by running appropriate
> 'info' commands.

This is pretty much what Linux real-time queued I/O signals do.
It's ugly but works. :-)

-- Jamie