# Re: \[net-next RFC V5 4/5\] virtio\_net: multiqueue support

- From: Jason Wang \<hidden\>
- Date: 2012-07-06 07:43:45 
- List: netdev
- Page: https://ratatoskr.run/netdev/2012/07/3889556
- Thread: https://ratatoskr.run/netdev/2012/07/3888981/t.md

```text
On 07/06/2012 04:02 AM, Amos Kong wrote:
> 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<redacted>
>> ---
> ...
>
>>
>>   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.

Right, it's a typo, thanks.
>> +
>> +	num_queue_pairs = num_queues / 2;
> ...
>
```