Commit 6213f07c authored by Li RongQing's avatar Li RongQing Committed by David S. Miller
Browse files

virtio_net: skip RCU read lock by checking xdp_enabled of vi 



networking benchmark shows that __rcu_read_lock and
__rcu_read_unlock takes some cpu cycles, and we can avoid
calling them partially in virtio rx path by check xdp_enabled
of vi, and xdp is disabled most of time

Signed-off-by: default avatarLi RongQing <lirongqing@baidu.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c0288ae8

drivers/net/virtio_net.c

+14 −0
Original line number Diff line number Diff line
@@ -734,6 +734,12 @@ static struct sk_buff *receive_small(struct net_device *dev, 
		dev->stats.rx_length_errors++;

		goto err_len;

	}



	if (likely(!vi->xdp_enabled)) {

		xdp_prog = NULL;

		goto skip_xdp;

	}



	rcu_read_lock();

	xdp_prog = rcu_dereference(rq->xdp_prog);

	if (xdp_prog) {
@@ -816,6 +822,7 @@ static struct sk_buff *receive_small(struct net_device *dev, 
	}

	rcu_read_unlock();



skip_xdp:

	skb = build_skb(buf, buflen);

	if (!skb) {

		put_page(page);
@@ -897,6 +904,12 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, 
		dev->stats.rx_length_errors++;

		goto err_skb;

	}



	if (likely(!vi->xdp_enabled)) {

		xdp_prog = NULL;

		goto skip_xdp;

	}



	rcu_read_lock();

	xdp_prog = rcu_dereference(rq->xdp_prog);

	if (xdp_prog) {
@@ -1024,6 +1037,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, 
	}

	rcu_read_unlock();



skip_xdp:

	head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog,

			       metasize, headroom);

	curr_skb = head_skb;