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Re: [Qemu-devel] question on virtio
From: |
Jamie Lokier |
Subject: |
Re: [Qemu-devel] question on virtio |
Date: |
Thu, 6 May 2010 17:43:31 +0100 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
Michael S. Tsirkin wrote:
> Hi!
> I see this in virtio_ring.c:
>
> /* Put entry in available array (but don't update avail->idx *
> until they do sync). */
>
> Why is it done this way?
> It seems that updating the index straight away would be simpler, while
> this might allow the host to specilatively look up the buffer and handle
> it, without waiting for the kick.
Even better, if the host updates a location containing which index it
has seen recently, you can avoid the kick entirely during sustained
flows - just like your recent patch to avoid sending irqs to the
guest.
-- Jamie