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SubjectRe: [PATCH V6 2/3] virtio-net: split out clean affinity function
On 01/25/2013 11:28 AM, Jason Wang wrote:
> On 01/21/2013 07:25 PM, Wanlong Gao wrote:
>> Split out the clean affinity function to virtnet_clean_affinity().
>>
>> 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>
>> ---
>> V5->V6: NEW
>>
>> drivers/net/virtio_net.c | 67 +++++++++++++++++++++++++++---------------------
>> 1 file changed, 38 insertions(+), 29 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 70cd957..1a35a8c 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1016,48 +1016,57 @@ 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_clean_affinity(struct virtnet_info *vi, long hcpu)
>> {
>> int i;
>> int cpu;
>>
>> - /* In multiqueue mode, when the number of cpu is equal to the number of
>> - * queue pairs, we let the queue pairs to be private to one cpu by
>> - * setting the affinity hint to eliminate the contention.
>> - */
>> - if ((vi->curr_queue_pairs == 1 ||
>> - vi->max_queue_pairs != num_online_cpus()) && set) {
>> - if (vi->affinity_hint_set)
>> - set = false;
>> - else
>> - return;
>> - }
>> -
>> - if (set) {
>> - i = 0;
>> - for_each_online_cpu(cpu) {
>> - virtqueue_/set_affinity(vi->rq[i].vq, cpu);
>> - virtqueue_set_affinity(vi->sq[i].vq, cpu);
>> - *per_cpu_ptr(vi->vq_index, cpu) = i;
>> - i++;
>> - }
>> -
>> - vi->affinity_hint_set = true;
>> - } else {
>> - for(i = 0; i < vi->max_queue_pairs; i++) {
>> + if (vi->affinity_hint_set) {
>> + for (i = 0; i < vi->max_queue_pairs; i++) {
>> virtqueue_set_affinity(vi->rq[i].vq, -1);
>> virtqueue_set_affinity(vi->sq[i].vq, -1);
>> }
>>
>> 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;
>> + }
>>
>
> Some questions here:
>
> - Did we need reset the affinity of the queue here like the this?
>
> virtqueue_set_affinity(vi->sq[*per_cpu_ptr(vi->vq_index, hcpu)], -1);
> virtqueue_set_affinity(vi->rq[*per_cpu_ptr(vi->vq_index, hcpu)], -1);

I think no, we are going to unset the affinity of all the set queues,
include hcpu.

>
> - Looks like we need also reset the percpu index when
> vi->affinity_hint_set is false.

Yes, follow this and the comment on [1/3].

> - Does this really need this reset? Consider we're going to reset the
> percpu in CPU_DEAD?

I think resetting when CPU_DOWN_PREPARE can avoid selecting the wrong queue
on the dying CPU.

Thanks,
Wanlong Gao

>
> Thanks
>> vi->affinity_hint_set = false;
>> }
>> }
>>
>> +static void virtnet_set_affinity(struct virtnet_info *vi)
>> +{
>> + int i;
>> + int cpu;
>> +
>> + /* In multiqueue mode, when the number of cpu is equal to the number of
>> + * queue pairs, we let the queue pairs to be private to one cpu by
>> + * setting the affinity hint to eliminate the contention.
>> + */
>> + if (vi->curr_queue_pairs == 1 ||
>> + vi->max_queue_pairs != num_online_cpus()) {
>> + if (vi->affinity_hint_set)
>> + virtnet_clean_affinity(vi, -1);
>> + else
>> + return;
>> + }
>> +
>> + i = 0;
>> + for_each_online_cpu(cpu) {
>> + virtqueue_set_affinity(vi->rq[i].vq, cpu);
>> + virtqueue_set_affinity(vi->sq[i].vq, cpu);
>> + *per_cpu_ptr(vi->vq_index, cpu) = i;
>> + i++;
>> + }
>> +
>> + vi->affinity_hint_set = true;
>> +}
>> +
>> static void virtnet_get_ringparam(struct net_device *dev,
>> struct ethtool_ringparam *ring)
>> {
>> @@ -1105,7 +1114,7 @@ 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);
>> put_online_cpus();
>> }
>>
>> @@ -1274,7 +1283,7 @@ static void virtnet_del_vqs(struct virtnet_info *vi)
>> {
>> struct virtio_device *vdev = vi->vdev;
>>
>> - virtnet_set_affinity(vi, false);
>> + virtnet_clean_affinity(vi, -1);
>>
>> vdev->config->del_vqs(vdev);
>>
>> @@ -1398,7 +1407,7 @@ static int init_vqs(struct virtnet_info *vi)
>> goto err_free;
>>
>> get_online_cpus();
>> - virtnet_set_affinity(vi, true);
>> + virtnet_set_affinity(vi);
>> put_online_cpus();
>>
>> return 0;
>
>



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