From: Jamie Lokier <jamie@shareable.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
kvm@vger.kernel.org, qemu-devel@nongnu.org,
virtualization@lists.linux-foundation.org
Subject: Re: [Qemu-devel] question on virtio
Date: Thu, 6 May 2010 17:43:31 +0100 [thread overview]
Message-ID: <20100506164331.GF28512@shareable.org> (raw)
In-Reply-To: <20100505110947.GA27872@redhat.com>
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
WARNING: multiple messages have this Message-ID (diff)
From: Jamie Lokier <jamie@shareable.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
qemu-devel@nongnu.org, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: Re: [Qemu-devel] question on virtio
Date: Thu, 6 May 2010 17:43:31 +0100 [thread overview]
Message-ID: <20100506164331.GF28512@shareable.org> (raw)
In-Reply-To: <20100505110947.GA27872@redhat.com>
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
next prev parent reply other threads:[~2010-05-06 16:43 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-05 11:09 question on virtio Michael S. Tsirkin
2010-05-05 11:09 ` [Qemu-devel] " Michael S. Tsirkin
2010-05-05 19:40 ` Anthony Liguori
2010-05-05 19:40 ` Anthony Liguori
2010-05-05 19:40 ` [Qemu-devel] " Anthony Liguori
2010-05-05 20:59 ` Michael S. Tsirkin
2010-05-05 20:59 ` [Qemu-devel] " Michael S. Tsirkin
2010-05-05 20:59 ` Michael S. Tsirkin
2010-05-06 1:32 ` Rusty Russell
2010-05-06 1:32 ` [Qemu-devel] " Rusty Russell
2010-05-06 1:32 ` Rusty Russell
2010-05-06 16:43 ` Jamie Lokier [this message]
2010-05-06 16:43 ` [Qemu-devel] " Jamie Lokier
2010-05-06 16:43 ` Jamie Lokier
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