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Date: Wed, 24 Nov 2010 17:59:19 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20101124155919.GB29235@redhat.com>
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Subject: [Qemu-devel] Re: [PATCH 09/10] Exit loop if we have been there too
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org, Juan Quintela <quintela@redhat.com>

On Wed, Nov 24, 2010 at 04:16:04PM +0100, Paolo Bonzini wrote:
> On 11/24/2010 12:14 PM, Michael S. Tsirkin wrote:
> >>>  buffered_file timer runs each 100ms.  And we "try" to measure channel
> >>>  bandwidth from there.  If we are not able to run the timer, all the
> >>>  calculations are wrong, and then stalls happens.
> >
> >So the problem is the timer in the buffered file abstraction?
> >Why don't we just flush out data if the buffer is full?
> 
> It takes a lot to fill the buffer if you have many zero pages, and
> if that happens the guest is starved by the main loop filling the
> buffer.
> 
> Paolo

To solve starvation we really should return to main loop
as soon as possible, give io a chance to run.
The timer based hack is probably the best we can do by 0.14, though.

-- 
MST