On 01/07/2013 03:15 PM, Wanlong Gao wrote:
> 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.
> Adding the notifier block to virtnet_info is suggested by
> Jason, thank you.
>
> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
> Cc: Jason Wang <jasowang@xxxxxxxxxx>
> Cc: Eric Dumazet <erdnetdev@xxxxxxxxx>
> Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> Signed-off-by: Wanlong Gao <gaowanlong@xxxxxxxxxxxxxx>
> ---
> 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 b483fb5..9547b4c 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);
> @@ -123,6 +124,9 @@ 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 {
> @@ -1051,6 +1055,23 @@ 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;
> +}
> +
I think you'd better fix the .ndo_select_queue() as well (as Michael
said in your V1) since it currently uses smp processor id which may not
work very well in this case also.
Thanks
> static void virtnet_get_ringparam(struct net_device *dev,
> struct ethtool_ringparam *ring)
> {
> @@ -1509,6 +1530,13 @@ 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)) {
> @@ -1553,6 +1581,8 @@ 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;
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