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>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 2f6fe9b6b17b..35c00c5ea02a 100644
--- 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;