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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: Li RongQing <lirongqing@baidu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Li RongQing 2021-10-09 17:32:43 +08:00 committed by David S. Miller
parent c0288ae8e6
commit 6213f07cb5
1 changed files with 14 additions and 0 deletions
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14
drivers/net/virtio_net.c
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@ -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;