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Re: [Qemu-devel] [4341] qemu: generate signals on tap I/O

From: Anders
Subject: Re: [Qemu-devel] [4341] qemu: generate signals on tap I/O
Date: Tue, 6 May 2008 10:35:03 +0200 (CEST)
User-agent: SquirrelMail/1.4.13

Anthony Liguori wrote:
> Anders wrote:
>> Anthony Liguori wrote:
>>> You're seeing improvement with normal QEMU?  Can you please post a
>>> description of what you're seeing improve with SIGIO.  SIGIO should
>>> really only slow things down.
>> I found this issue in KVM. I have not timed in QEMU, but the issue
>> seemed generic, so I posted it upstream.
> Right, this was an artifact of how KVM handled select.  It's not generic
> at all.

If that is true, then the SIGALRM IO handler must also be redundant?

> In KVM today, select() is in it's own thread so it will service IO
> immediately.  This makes SIGIO unnecessary (not quite correct yet but
> will be very soon).

Yes, you keep saying that. I think that work on a new implementation is
orthogonal to fixing the current one, though.


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