virtio-net: reset virtqueue affinity when doing cpu hotplug

Add a cpu notifier to virtio-net, so that we can reset the
virtqueue affinity if the cpu hotplug happens. It improve
the performance through enabling or disabling the virtqueue
affinity after doing cpu hotplug.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Eric Dumazet <erdnetdev@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: virtualization@lists.linux-foundation.org
Cc: netdev@vger.kernel.org
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 2f6fe9b..35c00c5 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -26,6 +26,7 @@
 #include <linux/scatterlist.h>
 #include <linux/if_vlan.h>
 #include <linux/slab.h>
+#include <linux/cpu.h>
 
 static int napi_weight = 128;
 module_param(napi_weight, int, 0444);
@@ -126,6 +127,9 @@ struct virtnet_info {
 
        /* Per-cpu variable to show the mapping from CPU to virtqueue */
        int __percpu *vq_index;
+
+       /* CPU hot plug notifier */
+       struct notifier_block nb;
 };
 
 struct skb_vnet_hdr {
@@ -1067,6 +1071,26 @@ static void virtnet_set_affinity(struct virtnet_info *vi)
        vi->affinity_hint_set = true;
 }
 
+static int virtnet_cpu_callback(struct notifier_block *nfb,
+                               unsigned long action, void *hcpu)
+{
+       struct virtnet_info *vi = container_of(nfb, struct virtnet_info, nb);
+
+       switch(action & ~CPU_TASKS_FROZEN) {
+       case CPU_ONLINE:
+       case CPU_DOWN_FAILED:
+       case CPU_DEAD:
+               virtnet_set_affinity(vi);
+               break;
+       case CPU_DOWN_PREPARE:
+               virtnet_clean_affinity(vi, (long)hcpu);
+               break;
+       default:
+               break;
+       }
+       return NOTIFY_OK;
+}
+
 static void virtnet_get_ringparam(struct net_device *dev,
                                struct ethtool_ringparam *ring)
 {
@@ -1541,6 +1565,13 @@ static int virtnet_probe(struct virtio_device *vdev)
                }
        }
 
+       vi->nb.notifier_call = &virtnet_cpu_callback;
+       err = register_hotcpu_notifier(&vi->nb);
+       if (err) {
+               pr_debug("virtio_net: registering cpu notifier failed\n");
+               goto free_recv_bufs;
+       }
+
        /* Assume link up if device can't report link status,
           otherwise get link status from config. */
        if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) {
@@ -1587,6 +1618,8 @@ static void virtnet_remove(struct virtio_device *vdev)
 {
        struct virtnet_info *vi = vdev->priv;
 
+       unregister_hotcpu_notifier(&vi->nb);
+
        /* Prevent config work handler from accessing the device. */
        mutex_lock(&vi->config_lock);
        vi->config_enable = false;