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 <ru...@rustcorp.com.au>
Cc: "Michael S. Tsirkin" <m...@redhat.com>
Cc: Jason Wang <jasow...@redhat.com>
Cc: Eric Dumazet <erdnet...@gmail.com>
Cc: virtualizat...@lists.linux-foundation.org
Cc: net...@vger.kernel.org
Signed-off-by: Wanlong Gao <gaowanl...@cn.fujitsu.com>
---
V4->V5:
New method to deal with the cpu hotplug actions (Rusty)
drivers/net/virtio_net.c | 50 ++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 44 insertions(+), 6 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 440b0eb..061f2c5 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 {
@@ -1016,7 +1020,7 @@ static int virtnet_vlan_rx_kill_vid(struct net_device
*dev, u16 vid)
return 0;
}
-static void virtnet_set_affinity(struct virtnet_info *vi, bool set)
+static void virtnet_set_affinity(struct virtnet_info *vi, bool set, long hcpu)
{
int i;
int cpu;
@@ -1026,7 +1030,8 @@ static void virtnet_set_affinity(struct virtnet_info *vi,
bool set)
* setting the affinity hint to eliminate the contention.
*/
if ((vi->curr_queue_pairs == 1 ||
- vi->max_queue_pairs != num_online_cpus()) && set) {
+ vi->max_queue_pairs != num_online_cpus() - ((hcpu == -1) ? 0 : 1))
+ && set) {
if (vi->affinity_hint_set)
set = false;
else
@@ -1036,6 +1041,8 @@ static void virtnet_set_affinity(struct virtnet_info *vi,
bool set)
if (set) {
i = 0;
for_each_online_cpu(cpu) {
+ if (cpu == hcpu)
+ continue;
virtqueue_set_affinity(vi->rq[i].vq, cpu);
virtqueue_set_affinity(vi->sq[i].vq, cpu);
*per_cpu_ptr(vi->vq_index, cpu) = i;
@@ -1050,14 +1057,36 @@ static void virtnet_set_affinity(struct virtnet_info
*vi, bool set)
}
i = 0;
- for_each_online_cpu(cpu)
+ for_each_online_cpu(cpu) {
+ if (cpu == hcpu)
+ continue;
*per_cpu_ptr(vi->vq_index, cpu) =
++i % vi->curr_queue_pairs;
+ }
vi->affinity_hint_set = false;
}
}
+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:
+ virtnet_set_affinity(vi, true, -1);
+ break;
+ case CPU_DOWN_PREPARE:
+ virtnet_set_affinity(vi, true, (long)hcpu);
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
static void virtnet_get_ringparam(struct net_device *dev,
struct ethtool_ringparam *ring)
{
@@ -1105,7 +1134,7 @@ static int virtnet_set_channels(struct net_device *dev,
netif_set_real_num_rx_queues(dev, queue_pairs);
get_online_cpus();
- virtnet_set_affinity(vi, true);
+ virtnet_set_affinity(vi, true, -1);
put_online_cpus();
}
@@ -1275,7 +1304,7 @@ static void virtnet_del_vqs(struct virtnet_info *vi)
struct virtio_device *vdev = vi->vdev;
get_online_cpus();
- virtnet_set_affinity(vi, false);
+ virtnet_set_affinity(vi, false, -1);
put_online_cpus();
vdev->config->del_vqs(vdev);
@@ -1400,7 +1429,7 @@ static int init_vqs(struct virtnet_info *vi)
goto err_free;
get_online_cpus();
- virtnet_set_affinity(vi, true);
+ virtnet_set_affinity(vi, true, -1);
put_online_cpus();
return 0;
@@ -1534,6 +1563,13 @@ 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)) {
@@ -1580,6 +1616,8 @@ 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
--
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