Update avail index immediately instead of upon kick: for virtio-net RX this helps parallelism with the host.
Signed-off-by: Michael S. Tsirkin <[email protected]> --- drivers/virtio/virtio_ring.c | 15 +++++---------- 1 files changed, 5 insertions(+), 10 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 059e02d..507d6eb 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -86,8 +86,6 @@ struct vring_virtqueue unsigned int num_free; /* Head of free buffer list. */ unsigned int free_head; - /* Number we've added since last sync. */ - unsigned int num_added; /* Last used index we've seen. */ u16 last_used_idx; @@ -224,8 +222,12 @@ add_head: /* Put entry in available array (but don't update avail->idx until they * do sync). FIXME: avoid modulus here? */ - avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num; + avail = vq->vring.avail->idx % vq->vring.num; vq->vring.avail->ring[avail] = head; + /* Descriptors and available array need to be set before we expose the + * new available array entries. */ + virtio_wmb(); + vq->vring.avail->idx++; pr_debug("Added buffer head %i to %p\n", head, vq); END_USE(vq); @@ -238,12 +240,6 @@ void virtqueue_kick(struct virtqueue *_vq) { struct vring_virtqueue *vq = to_vvq(_vq); START_USE(vq); - /* Descriptors and available array need to be set before we expose the - * new available array entries. */ - virtio_wmb(); - - vq->vring.avail->idx += vq->num_added; - vq->num_added = 0; /* Need to update avail index before checking if we should notify */ virtio_mb(); @@ -430,7 +426,6 @@ struct virtqueue *vring_new_virtqueue(unsigned int num, vq->notify = notify; vq->broken = false; vq->last_used_idx = 0; - vq->num_added = 0; list_add_tail(&vq->vq.list, &vdev->vqs); #ifdef DEBUG vq->in_use = false; -- 1.7.5.53.gc233e -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
