Commit 75eefc6c authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller

tcp: tsq: add a shortcut in tcp_small_queue_check()

Always allow the two first skbs in write queue to be sent,
regardless of sk_wmem_alloc/sk_pacing_rate values.

This helps a lot in situations where TX completions are delayed either
because of driver latencies or softirq latencies.

Test is done with no cache line misses.
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a9b204d1
...@@ -2091,6 +2091,15 @@ static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb, ...@@ -2091,6 +2091,15 @@ static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
limit <<= factor; limit <<= factor;
if (atomic_read(&sk->sk_wmem_alloc) > limit) { if (atomic_read(&sk->sk_wmem_alloc) > limit) {
/* Always send the 1st or 2nd skb in write queue.
* No need to wait for TX completion to call us back,
* after softirq/tasklet schedule.
* This helps when TX completions are delayed too much.
*/
if (skb == sk->sk_write_queue.next ||
skb->prev == sk->sk_write_queue.next)
return false;
set_bit(TSQ_THROTTLED, &tcp_sk(sk)->tsq_flags); set_bit(TSQ_THROTTLED, &tcp_sk(sk)->tsq_flags);
/* It is possible TX completion already happened /* It is possible TX completion already happened
* before we set TSQ_THROTTLED, so we must * before we set TSQ_THROTTLED, so we must
......
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