From: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public•gmane.org>
To: "Michael S. Tsirkin"
<mst-H+wXaHxf7aLQT0dZR+AlfA@public•gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public•gmane.org
Cc: Krishna Kumar <krkumar2-xthvdsQ13ZrQT0dZR+AlfA@public•gmane.org>,
Carsten Otte <cotte-tA70FqPdS9bQT0dZR+AlfA@public•gmane.org>,
lguest-uLR06cmDAlY/bJ5BZ2RsiQ@public•gmane.org,
Shirley Ma <xma-r/Jw6+rmf7HQT0dZR+AlfA@public•gmane.org>,
kvm-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
linux-s390-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
habanero-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public•gmane.org,
Heiko Carstens
<heiko.carstens-tA70FqPdS9bQT0dZR+AlfA@public•gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public•gmane.org,
steved-r/Jw6+rmf7HQT0dZR+AlfA@public•gmane.org,
Christian Borntraeger
<borntraeger-tA70FqPdS9bQT0dZR+AlfA@public•gmane.org>,
Tom Lendacky
<tahm-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public•gmane.org>,
Martin Schwidefsky
<schwidefsky-tA70FqPdS9bQT0dZR+AlfA@public•gmane.org>,
linux390-tA70FqPdS9bQT0dZR+AlfA@public•gmane.org
Subject: Re: [PATCH 09/18] virtio: use avail_event index
Date: Mon, 09 May 2011 14:03:26 +0930 [thread overview]
Message-ID: <874o54h4rt.fsf@rustcorp.com.au> (raw)
In-Reply-To: <8bba6a0a8eee17e741c5155b04ff1b1c9f34bf94.1304541919.git.mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
On Wed, 4 May 2011 23:51:47 +0300, "Michael S. Tsirkin" <mst-H+wXaHxf7aLQT0dZR+AlfA@public•gmane.org> wrote:
> Use the new avail_event feature to reduce the number
> of exits from the guest.
Figures here would be nice :)
> @@ -228,6 +237,12 @@ add_head:
> * new available array entries. */
> virtio_wmb();
> vq->vring.avail->idx++;
> + /* If the driver never bothers to kick in a very long while,
> + * avail index might wrap around. If that happens, invalidate
> + * kicked_avail index we stored. TODO: make sure all drivers
> + * kick at least once in 2^16 and remove this. */
> + if (unlikely(vq->vring.avail->idx == vq->kicked_avail))
> + vq->kicked_avail_valid = true;
If they don't, they're already buggy. Simply do:
WARN_ON(vq->vring.avail->idx == vq->kicked_avail);
> +static bool vring_notify(struct vring_virtqueue *vq)
> +{
> + u16 old, new;
> + bool v;
> + if (!vq->event)
> + return !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY);
> +
> + v = vq->kicked_avail_valid;
> + old = vq->kicked_avail;
> + new = vq->kicked_avail = vq->vring.avail->idx;
> + vq->kicked_avail_valid = true;
> + if (unlikely(!v))
> + return true;
This is the only place you actually used kicked_avail_valid. Is it
possible to initialize it in such a way that you can remove this?
> @@ -482,6 +517,8 @@ void vring_transport_features(struct virtio_device *vdev)
> break;
> case VIRTIO_RING_F_USED_EVENT_IDX:
> break;
> + case VIRTIO_RING_F_AVAIL_EVENT_IDX:
> + break;
> default:
> /* We don't understand this bit. */
> clear_bit(i, vdev->features);
Does this belong in a prior patch?
Thanks,
Rusty.
next prev parent reply other threads:[~2011-05-09 4:33 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-04 20:50 [PATCH 00/18] virtio and vhost-net performance enhancements Michael S. Tsirkin
2011-05-04 20:50 ` [PATCH 01/18] virtio: 64 bit features Michael S. Tsirkin
2011-05-04 20:50 ` [PATCH 02/18] virtio_test: update for " Michael S. Tsirkin
2011-05-04 20:50 ` [PATCH 03/18] vhost: fix " Michael S. Tsirkin
2011-05-04 20:51 ` [PATCH 04/18] virtio: don't delay avail index update Michael S. Tsirkin
2011-05-04 20:51 ` [PATCH 05/18] virtio: used event index interface Michael S. Tsirkin
2011-05-04 21:56 ` Tom Lendacky
2011-05-05 9:38 ` Michael S. Tsirkin
2011-05-04 20:51 ` [PATCH 06/18] virtio_ring: avail " Michael S. Tsirkin
2011-05-09 4:13 ` Rusty Russell
[not found] ` <87aaewh5pg.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
2011-05-15 12:47 ` Michael S. Tsirkin
[not found] ` <20110515124727.GA24932-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-05-16 6:23 ` Rusty Russell
[not found] ` <87k4drduzs.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
2011-05-17 6:00 ` Michael S. Tsirkin
[not found] ` <20110517060052.GB26989-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-05-18 0:08 ` Rusty Russell
2011-05-04 20:51 ` [PATCH 07/18] virtio ring: inline function to check for events Michael S. Tsirkin
2011-05-05 8:34 ` Stefan Hajnoczi
2011-05-05 8:56 ` Michael S. Tsirkin
2011-05-04 20:51 ` [PATCH 08/18] virtio_ring: support for used_event idx feature Michael S. Tsirkin
[not found] ` <dd16b9f3bad847b0eadc7f94368e27982c1a7560.1304541919.git.mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-05-09 4:17 ` Rusty Russell
[not found] ` <878vugh5ib.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
2011-05-15 12:47 ` Michael S. Tsirkin
2011-05-04 20:51 ` [PATCH 09/18] virtio: use avail_event index Michael S. Tsirkin
2011-05-04 21:58 ` Tom Lendacky
2011-05-05 9:34 ` Michael S. Tsirkin
[not found] ` <8bba6a0a8eee17e741c5155b04ff1b1c9f34bf94.1304541919.git.mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-05-09 4:33 ` Rusty Russell [this message]
[not found] ` <874o54h4rt.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
2011-05-15 13:55 ` Michael S. Tsirkin
[not found] ` <20110515135541.GF24932-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-05-16 7:12 ` Rusty Russell
[not found] ` <87ei3zdsq2.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
2011-05-17 6:10 ` Michael S. Tsirkin
[not found] ` <20110517061031.GC26989-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-05-18 0:19 ` Rusty Russell
[not found] ` <87tycsn9lt.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
2011-05-18 5:43 ` Michael S. Tsirkin
2011-05-19 7:27 ` Michael S. Tsirkin
2011-05-17 16:23 ` Tom Lendacky
2011-05-04 20:51 ` [PATCH 10/18] vhost: utilize used_event index Michael S. Tsirkin
2011-05-04 20:52 ` [PATCH 11/18] vhost: support avail_event idx Michael S. Tsirkin
2011-05-04 20:52 ` [PATCH 12/18] virtio_test: support used_event index Michael S. Tsirkin
2011-05-04 20:52 ` [PATCH 13/18] virtio_test: avail_event index support Michael S. Tsirkin
2011-05-04 20:52 ` [PATCH 14/18] virtio: add api for delayed callbacks Michael S. Tsirkin
[not found] ` <64d47c628b3fdc0ac156aed4be182933d8bcc0db.1304541919.git.mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-05-09 5:57 ` Rusty Russell
[not found] ` <871v08h0vm.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
2011-05-15 12:48 ` Michael S. Tsirkin
[not found] ` <20110515124818.GD24932-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-05-16 7:13 ` Rusty Russell
[not found] ` <87boz3dsoe.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
2011-05-19 7:24 ` Michael S. Tsirkin
[not found] ` <20110519072412.GA31253-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-05-20 7:43 ` Rusty Russell
2011-05-04 20:52 ` [PATCH 15/18] virtio_net: delay TX callbacks Michael S. Tsirkin
2011-05-04 20:52 ` [PATCH 16/18] virtio_ring: Add capacity check API Michael S. Tsirkin
2011-05-04 20:53 ` [PATCH 17/18] virtio_net: fix TX capacity checks using new API Michael S. Tsirkin
2011-05-04 20:53 ` [PATCH 18/18] virtio_net: limit xmit polling Michael S. Tsirkin
2011-05-05 15:07 ` [PATCH 0/3] virtio and vhost-net performance enhancements Michael S. Tsirkin
2011-05-05 15:08 ` [PATCH 1/3] virtio: fix avail event support Michael S. Tsirkin
2011-05-05 15:08 ` [PATCH 2/3] virtio_ring: check used_event offset Michael S. Tsirkin
2011-05-05 15:08 ` [PATCH 3/3] virtio_ring: need_event api comment fix Michael S. Tsirkin
[not found] ` <c8b6d8a8df4927826d0024fceeb68726c50d0b1a.1304605817.git.mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-05-09 5:59 ` Rusty Russell
2011-05-11 17:10 ` [PATCH 00/18] virtio and vhost-net performance enhancements Krishna Kumar2
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