On Wed, Mar 16, 2011 at 05:12:55PM -0700, Shirley Ma wrote: > Signed-off-by: Shirley Ma <x...@us.ibm.com> > --- > drivers/net/virtio_net.c | 39 ++++++++++++++++++++------------------- > 1 files changed, 20 insertions(+), 19 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 82dba5a..c603daa 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -23,6 +23,7 @@ > #include <linux/module.h> > #include <linux/virtio.h> > #include <linux/virtio_net.h> > +#include <linux/virtio_ring.h> > #include <linux/scatterlist.h> > #include <linux/if_vlan.h> > #include <linux/slab.h> > @@ -509,19 +510,18 @@ 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; > > while ((skb = virtqueue_get_buf(vi->svq, &len)) != NULL) { > pr_debug("Sent skb %p\n", skb); > vi->dev->stats.tx_bytes += skb->len; > vi->dev->stats.tx_packets++; > - tot_sgs += skb_vnet_hdr(skb)->num_sg; > dev_kfree_skb_any(skb); > } > - return tot_sgs; > + return; > } > > static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb) > @@ -574,11 +574,26 @@ static int xmit_skb(struct virtnet_info *vi, struct > sk_buff *skb) > static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) > { > struct virtnet_info *vi = netdev_priv(dev); > + bool drop; > + bool indirect = virtio_has_feature(vi->vdev, > + VIRTIO_RING_F_INDIRECT_DESC); > int capacity; > > /* Free up any pending old buffers before queueing new ones. */ > free_old_xmit_skbs(vi); > - > + capacity = virtqueue_get_capacity(vi->svq); > + > + /* Drop packet instead of stop queue for better performance */ > + drop = (capacity == 0 && indirect) || > + ((capacity < MAX_SKB_FRAGS + 2) && !indirect); > + if (unlikely(drop)) { > + dev->stats.tx_fifo_errors++; > + dev_warn(&dev->dev, "Unexpected TX queue failure: %d\n", > + capacity); > + dev->stats.tx_dropped++; > + kfree_skb(skb); > + return NETDEV_TX_OK; > + } > /* Try to transmit */ > capacity = xmit_skb(vi, skb);
So, this just tries to make sure there's enough space for max packet in the ring, if not - drop and return OK. Why bother checking beforehand though? If that's what we want to do, we can just call add_buf and see if it fails? > @@ -605,20 +620,6 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, > struct net_device *dev) > skb_orphan(skb); > nf_reset(skb); > > - /* Apparently nice girls don't return TX_BUSY; stop the queue > - * before it gets out of hand. Naturally, this wastes entries. */ > - if (capacity < 2+MAX_SKB_FRAGS) { > - netif_stop_queue(dev); > - if (unlikely(!virtqueue_enable_cb(vi->svq))) { > - /* More just got used, free them then recheck. */ > - capacity += free_old_xmit_skbs(vi); > - if (capacity >= 2+MAX_SKB_FRAGS) { > - netif_start_queue(dev); > - virtqueue_disable_cb(vi->svq); > - } > - } > - } > - > return NETDEV_TX_OK; > } > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html