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authorMichael S. Tsirkin <mst@redhat.com>2012-10-16 23:56:14 +1030
committerRusty Russell <rusty@rustcorp.com.au>2012-12-18 15:20:32 +1030
commit6ee57bcc1e61d39c0579438055bc84087210f9b6 (patch)
tree2cae790fe378aa4be4419e40ae13f2a4e4b4d8c5
parent06ca287dbac9cc19d04ac2901b8c4882c03795ff (diff)
downloadop-kernel-dev-6ee57bcc1e61d39c0579438055bc84087210f9b6.zip
op-kernel-dev-6ee57bcc1e61d39c0579438055bc84087210f9b6.tar.gz
virtio-net: correct capacity math on ring full
Capacity math on ring full is wrong: we are looking at num_sg but that might be optimistic because of indirect buffer use. The implementation also penalizes fast path with extra memory accesses for the benefit of ring full condition handling which is slow path. It's easy to query ring capacity so let's do just that. This change also makes it easier to move vnet header for tx around as follow-up patch does. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Michael S. Tsirkin <mst@redhat.com>
-rw-r--r--drivers/net/virtio_net.c9
1 files changed, 4 insertions, 5 deletions
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index cbf8b06..3db6586 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -557,10 +557,10 @@ again:
return received;
}
-static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
+static void free_old_xmit_skbs(struct virtnet_info *vi)
{
struct sk_buff *skb;
- unsigned int len, tot_sgs = 0;
+ unsigned int len;
struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
while ((skb = virtqueue_get_buf(vi->svq, &len)) != NULL) {
@@ -571,10 +571,8 @@ static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
stats->tx_packets++;
u64_stats_update_end(&stats->tx_syncp);
- tot_sgs += skb_vnet_hdr(skb)->num_sg;
dev_kfree_skb_any(skb);
}
- return tot_sgs;
}
static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
@@ -664,7 +662,8 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
netif_stop_queue(dev);
if (unlikely(!virtqueue_enable_cb_delayed(vi->svq))) {
/* More just got used, free them then recheck. */
- capacity += free_old_xmit_skbs(vi);
+ free_old_xmit_skbs(vi);
+ capacity = vi->svq->num_free;
if (capacity >= 2+MAX_SKB_FRAGS) {
netif_start_queue(dev);
virtqueue_disable_cb(vi->svq);
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