[PATCH V3 2/2] virtio-net: reset virtqueue affinity when doing cpu hotplug

Wanlong Gao
2013-01-08T10:07:34Z

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: virtualization@lists.linux-foundation.org
Cc: netdev@vger.kernel.org
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
---
drivers/net/virtio_net.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index a77f86c..31a25db 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);
@@ -125,6 +126,9 @@ struct virtnet_info {

/* Does the affinity hint is set for virtqueues? */
bool affinity_hint_set;
+
+ /* CPU hot plug notifier */
+ struct notifier_block nb;
};

struct skb_vnet_hdr {
@@ -1057,6 +1061,23 @@ static void virtnet_set_affinity(struct virtnet_info *vi, bool set)
}
}

+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) {
+ case CPU_ONLINE:
+ case CPU_ONLINE_FROZEN:
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ virtnet_set_affinity(vi, true);
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
static void virtnet_get_ringparam(struct net_device *dev,
struct ethtool_ringparam *ring)
{
@@ -1518,6 +1539,13 @@ 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)) {
@@ -1562,6 +1590,8 @@ 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;
--
1.8.1