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Date: Fri, 17 Jun 2011 12:13:14 -0700
From: Stephen Hemminger <shemminger@...tta.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Rusty Russell <rusty@...tcorp.com.au>,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [PATCH] virtio-net: per cpu 64 bit stats
On Wed, 15 Jun 2011 21:33:16 +0300
"Michael S. Tsirkin" <mst@...hat.com> wrote:
> On Wed, Jun 15, 2011 at 11:43:37AM -0400, Stephen Hemminger wrote:
> > Use per-cpu variables to maintain 64 bit statistics.
> > Compile tested only.
> >
> > Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
>
> Interesting. Does this help speed at all?
>
> > --- a/drivers/net/virtio_net.c 2011-06-14 15:18:46.448596355 -0400
> > +++ b/drivers/net/virtio_net.c 2011-06-15 09:54:22.914426067 -0400
> > @@ -40,6 +40,15 @@ module_param(gso, bool, 0444);
> >
> > #define VIRTNET_SEND_COMMAND_SG_MAX 2
> >
> > +struct virtnet_stats {
> > + struct u64_stats_sync syncp;
> > + u64 tx_bytes;
> > + u64 tx_packets;
> > +
> > + u64 rx_bytes;
> > + u64 rx_packets;
> > +};
> > +
> > struct virtnet_info {
> > struct virtio_device *vdev;
> > struct virtqueue *rvq, *svq, *cvq;
> > @@ -56,6 +65,9 @@ struct virtnet_info {
> > /* Host will merge rx buffers for big packets (shake it! shake it!) */
> > bool mergeable_rx_bufs;
> >
> > + /* Active statistics */
> > + struct virtnet_stats __percpu *stats;
> > +
> > /* Work struct for refilling if we run low on memory. */
> > struct delayed_work refill;
> >
> > @@ -209,7 +221,6 @@ static int receive_mergeable(struct virt
> > skb->dev->stats.rx_length_errors++;
> > return -EINVAL;
> > }
> > -
> > page = virtqueue_get_buf(vi->rvq, &len);
> > if (!page) {
> > pr_debug("%s: rx error: %d buffers missing\n",
> > @@ -217,6 +228,7 @@ static int receive_mergeable(struct virt
> > skb->dev->stats.rx_length_errors++;
> > return -EINVAL;
> > }
> > +
> > if (len > PAGE_SIZE)
> > len = PAGE_SIZE;
> >
>
> Let's not tweak whitespace unnecessarily.
>
> > @@ -230,6 +242,7 @@ static int receive_mergeable(struct virt
> > static void receive_buf(struct net_device *dev, void *buf, unsigned int len)
> > {
> > struct virtnet_info *vi = netdev_priv(dev);
> > + struct virtnet_stats __percpu *stats = this_cpu_ptr(vi->stats);
> > struct sk_buff *skb;
> > struct page *page;
> > struct skb_vnet_hdr *hdr;
> > @@ -265,8 +278,11 @@ static void receive_buf(struct net_devic
> >
> > hdr = skb_vnet_hdr(skb);
> > skb->truesize += skb->data_len;
> > - dev->stats.rx_bytes += skb->len;
> > - dev->stats.rx_packets++;
> > +
> > + u64_stats_update_begin(&stats->syncp);
> > + stats->rx_bytes += skb->len;
> > + stats->rx_packets++;
> > + u64_stats_update_begin(&stats->syncp);
> >
> > if (hdr->hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
> > pr_debug("Needs csum!\n");
> > @@ -515,11 +531,16 @@ static unsigned int free_old_xmit_skbs(s
> > {
> > struct sk_buff *skb;
> > unsigned int len, tot_sgs = 0;
> > + struct virtnet_stats __percpu *stats = this_cpu_ptr(vi->stats);
> >
> > 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++;
> > +
> > + u64_stats_update_begin(&stats->syncp);
> > + stats->tx_bytes += skb->len;
> > + stats->tx_packets++;
> > + u64_stats_update_begin(&stats->syncp);
> > +
> > tot_sgs += skb_vnet_hdr(skb)->num_sg;
> > dev_kfree_skb_any(skb);
> > }
> > @@ -641,6 +662,40 @@ static int virtnet_set_mac_address(struc
> > return 0;
> > }
> >
> > +static struct rtnl_link_stats64 *virtnet_stats(struct net_device *dev,
> > + struct rtnl_link_stats64 *tot)
> > +{
> > + struct virtnet_info *vi = netdev_priv(dev);
> > + int cpu;
> > + unsigned int start;
> > +
> > + for_each_possible_cpu(cpu) {
> > + struct virtnet_stats __percpu *stats
> > + = per_cpu_ptr(vi->stats, cpu);
> > + u64 tpackets, tbytes, rpackets, rbytes;
> > +
> > + do {
> > + start = u64_stats_fetch_begin(&stats->syncp);
> > + tpackets = stats->tx_packets;
> > + tbytes = stats->tx_bytes;
> > + rpackets = stats->rx_packets;
> > + rbytes = stats->rx_bytes;
> > + } while (u64_stats_fetch_retry(&stats->syncp, start));
> > +
> > + tot->rx_packets += rpackets;
> > + tot->tx_packets += tpackets;
> > + tot->rx_bytes += rbytes;
> > + tot->tx_bytes += tbytes;
> > + }
> > +
> > + tot->tx_dropped = dev->stats.tx_dropped;
> > + tot->rx_dropped = dev->stats.rx_dropped;
> > + tot->rx_length_errors = dev->stats.rx_length_errors;
> > + tot->rx_frame_errors = dev->stats.rx_frame_errors;
> > +
> > + return tot;
> > +}
> > +
> > #ifdef CONFIG_NET_POLL_CONTROLLER
> > static void virtnet_netpoll(struct net_device *dev)
> > {
> > @@ -650,6 +705,14 @@ static void virtnet_netpoll(struct net_d
> > }
> > #endif
> >
> > +static void virtnet_free(struct net_device *dev)
> > +{
> > + struct virtnet_info *vi = netdev_priv(dev);
> > +
> > + free_percpu(vi->stats);
> > + free_netdev(dev);
> > +}
> > +
> > static int virtnet_open(struct net_device *dev)
> > {
> > struct virtnet_info *vi = netdev_priv(dev);
> > @@ -835,6 +898,7 @@ static const struct net_device_ops virtn
> > .ndo_set_mac_address = virtnet_set_mac_address,
> > .ndo_set_rx_mode = virtnet_set_rx_mode,
> > .ndo_change_mtu = virtnet_change_mtu,
> > + .ndo_get_stats64 = virtnet_stats,
> > .ndo_vlan_rx_add_vid = virtnet_vlan_rx_add_vid,
> > .ndo_vlan_rx_kill_vid = virtnet_vlan_rx_kill_vid,
> > #ifdef CONFIG_NET_POLL_CONTROLLER
> > @@ -895,6 +959,8 @@ static int virtnet_probe(struct virtio_d
> > /* Set up network device as normal. */
> > dev->netdev_ops = &virtnet_netdev;
> > dev->features = NETIF_F_HIGHDMA;
> > + dev->destructor = virtnet_free;
> > +
> > SET_ETHTOOL_OPS(dev, &virtnet_ethtool_ops);
> > SET_NETDEV_DEV(dev, &vdev->dev);
> >
> > @@ -939,6 +1005,11 @@ static int virtnet_probe(struct virtio_d
> > vi->vdev = vdev;
> > vdev->priv = vi;
> > vi->pages = NULL;
> > + vi->stats = alloc_percpu(struct virtnet_stats);
> > + err = -ENOMEM;
> > + if (vi->stats == NULL)
> > + goto free;
> > +
> > INIT_DELAYED_WORK(&vi->refill, refill_work);
> > sg_init_table(vi->rx_sg, ARRAY_SIZE(vi->rx_sg));
> > sg_init_table(vi->tx_sg, ARRAY_SIZE(vi->tx_sg));
> > @@ -958,7 +1029,7 @@ static int virtnet_probe(struct virtio_d
> >
> > err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names);
> > if (err)
> > - goto free;
> > + goto free_stats;
> >
> > vi->rvq = vqs[0];
> > vi->svq = vqs[1];
> > @@ -1003,6 +1074,8 @@ unregister:
> > cancel_delayed_work_sync(&vi->refill);
> > free_vqs:
> > vdev->config->del_vqs(vdev);
> > +free_stats:
> > + free_percpu(vi->stats);
> > free:
> > free_netdev(dev);
> > return err;
Haven't done any performance tests on this.
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