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Message-ID: <20110615183316.GB7197@redhat.com>
Date: Wed, 15 Jun 2011 21:33:16 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Stephen Hemminger <shemminger@...tta.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, 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;
--
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