virtio-net: fill only rx queues which are being used

Due to MQ support we may allocate a whole bunch of rx queues but
never use them. With this patch we'll safe the space used by
the receive buffers until they are actually in use:

sh-4.2# free -h
             total       used       free     shared    buffers     cached
Mem:          490M        35M       455M         0B         0B       4.1M
-/+ buffers/cache:        31M       459M
Swap:           0B         0B         0B
sh-4.2# ethtool -L eth0 combined 8
sh-4.2# free -h
             total       used       free     shared    buffers     cached
Mem:          490M       162M       327M         0B         0B       4.1M
-/+ buffers/cache:       158M       331M
Swap:           0B         0B         0B

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 10 insertions, 5 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index d88d4366d9ac..b082e1c39031 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -581,7 +581,7 @@ static void refill_work(struct work_struct *work)
         bool still_empty;
         int i;
 
-        for (i = 0; i < vi->max_queue_pairs; i++) {
+        for (i = 0; i < vi->curr_queue_pairs; i++) {
                 struct receive_queue *rq = &vi->rq[i];
 
                 napi_disable(&rq->napi);
@@ -636,7 +636,7 @@ static int virtnet_open(struct net_device *dev)
         struct virtnet_info *vi = netdev_priv(dev);
         int i;
 
-        for (i = 0; i < vi->max_queue_pairs; i++) {
+        for (i = 0; i < vi->curr_queue_pairs; i++) {
                 /* Make sure we have some buffers: if oom use wq. */
                 if (!try_fill_recv(&vi->rq[i], GFP_KERNEL))
                         schedule_delayed_work(&vi->refill, 0);
@@ -900,6 +900,7 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
         struct scatterlist sg;
         struct virtio_net_ctrl_mq s;
         struct net_device *dev = vi->dev;
+        int i;
 
         if (!vi->has_cvq || !virtio_has_feature(vi->vdev, VIRTIO_NET_F_MQ))
                 return 0;
@@ -912,8 +913,12 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
                 dev_warn(&dev->dev, "Fail to set num of queue pairs to %d\n",
                          queue_pairs);
                 return -EINVAL;
-        } else
+        } else {
+                for (i = vi->curr_queue_pairs; i < queue_pairs; i++)
+                        if (!try_fill_recv(&vi->rq[i], GFP_KERNEL))
+                                schedule_delayed_work(&vi->refill, 0);
                 vi->curr_queue_pairs = queue_pairs;
+        }
 
         return 0;
 }
@@ -1566,7 +1571,7 @@ static int virtnet_probe(struct virtio_device *vdev)
         }
 
         /* Last of all, set up some receive buffers. */
-        for (i = 0; i < vi->max_queue_pairs; i++) {
+        for (i = 0; i < vi->curr_queue_pairs; i++) {
                 try_fill_recv(&vi->rq[i], GFP_KERNEL);
 
                 /* If we didn't even get one input buffer, we're useless. */
@@ -1690,7 +1695,7 @@ static int virtnet_restore(struct virtio_device *vdev)
 
         netif_device_attach(vi->dev);
 
-        for (i = 0; i < vi->max_queue_pairs; i++)
+        for (i = 0; i < vi->curr_queue_pairs; i++)
                 if (!try_fill_recv(&vi->rq[i], GFP_KERNEL))
                         schedule_delayed_work(&vi->refill, 0);