On 2014/2/11 23:43, Michael S. Tsirkin wrote:
On Tue, Feb 11, 2014 at 10:58:52PM +0800, Qin Chuanyu wrote:
udp packet use 2 buffers at least, one for vnet_hdr and
one for skb->data.
Not really, we use 1 buffer now with vnet_hdr inline with data.
I have found that there are related patch in Qemu,
Is there patch suit for vhost_net right now,
Or should I implement it myself ?
we could change the threshold from 2 to 3, so the udp packet
which data buff only using single desc will gain from this.
the guest would avoid from allocating memory dynamically.
the host would avoid from translating indirect desc.
Signed-off-by: Chuanyu Qin <qinchuanyu@xxxxxxxxxx>
Optimization patch without any performance data?
Such a change would need much more testing than that:
would have to try various workloads with -net and -blk at least.
---
drivers/virtio/virtio_ring.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 28b5338..88d008f 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -220,7 +220,7 @@ static inline int virtqueue_add(struct virtqueue *_vq,
/* If the host supports indirect descriptor tables, and we have multiple
* buffers, then go indirect. FIXME: tune this threshold */
- if (vq->indirect && total_sg > 1 && vq->vq.num_free) {
+ if (vq->indirect && total_sg > 2 && vq->vq.num_free) {
head = vring_add_indirect(vq, sgs, next, total_sg, total_out,
total_in,
out_sgs, in_sgs, gfp);
--
1.7.3.1.msysgit.0
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
