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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] threads on qemu
Date: Mon, 21 Jan 2008 16:00:39 +0000
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To: qemu-devel@nongnu.org
Cc: "C.W. Betts" <computers57@hotmail.com>

On Monday 21 January 2008, C.W. Betts wrote:
> I was thinking, maybe qemu could use threads for at least every processor
> it emulates (on emulated smp computers) and, at the most, every single
> device emulated.  This would help users who have multiple cores, but it
> might impact performance on those of us who don't.

Please read previous discussions on this mailing list.

I'd be surprised if putting device emulation  in a separate thread makes much 
difference. The really slow bits (waiting for IO to complete) are already 
asynchronous. Most other device accesses are very short, so you'd waste more 
time through synchronisation than you gain from putting them is a separate 
thread.

Splitting multiple CPUs into multiple threads is extremely hard to get right, 
especially when your host system provides less strict ordering and atomicity 
guarantees than those required by the guest system.

Paul