Re: [net-next RFC V5 4/5] virtio_net: multiqueue support
From: Amos Kong <hidden>
Date: 2012-07-05 20:03:43
Also in:
kvm, lkml, virtualization
On 07/05/2012 06:29 PM, Jason Wang wrote:
This patch converts virtio_net to a multi queue device. After negotiated VIRTIO_NET_F_MULTIQUEUE feature, the virtio device has many tx/rx queue pairs, and driver could read the number from config space. The driver expects the number of rx/tx queue paris is equal to the number of vcpus. To maximize the performance under this per-cpu rx/tx queue pairs, some optimization were introduced: - Txq selection is based on the processor id in order to avoid contending a lock whose owner may exits to host. - Since the txq/txq were per-cpu, affinity hint were set to the cpu that owns the queue pairs. Signed-off-by: Krishna Kumar <redacted> Signed-off-by: Jason Wang <jasowang@redhat.com> ---
...
static int virtnet_probe(struct virtio_device *vdev)
{
- int err;
+ int i, err;
struct net_device *dev;
struct virtnet_info *vi;
+ u16 num_queues, num_queue_pairs;
+
+ /* Find if host supports multiqueue virtio_net device */
+ err = virtio_config_val(vdev, VIRTIO_NET_F_MULTIQUEUE,
+ offsetof(struct virtio_net_config,
+ num_queues), &num_queues);
+
+ /* We need atleast 2 queue's */s/atleast/at least/
+ if (err || num_queues < 2) + num_queues = 2; + if (num_queues > MAX_QUEUES * 2) + num_queues = MAX_QUEUES;
num_queues = MAX_QUEUES * 2;
MAX_QUEUES is the limitation of RX or TX.
+ + num_queue_pairs = num_queues / 2;
... -- Amos.