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

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

net/ipv4/tcp_output.c

+9 −0
Original line number Diff line number Diff line
@@ -2091,6 +2091,15 @@ static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb, 
	limit <<= factor;



	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);

		/* It is possible TX completion already happened

		 * before we set TSQ_THROTTLED, so we must