Commit b223feb9 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: tsq: add shortcut in tcp_tasklet_func() 



Under high stress, I've seen tcp_tasklet_func() consuming
~700 usec, handling ~150 tcp sockets.

By setting TCP_TSQ_DEFERRED in tcp_wfree(), we give a chance
for other cpus/threads entering tcp_write_xmit() to grab it,
allowing tcp_tasklet_func() to skip sockets that already did
an xmit cycle.

In the future, we might give to ACK processing an increased
budget to reduce even more tcp_tasklet_func() amount of work.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 408f0a6c

net/ipv4/tcp_output.c

+12 −10
Original line number Diff line number Diff line
@@ -767,19 +767,19 @@ static void tcp_tasklet_func(unsigned long data) 
	list_for_each_safe(q, n, &list) {

		tp = list_entry(q, struct tcp_sock, tsq_node);

		list_del(&tp->tsq_node);

		clear_bit(TSQ_QUEUED, &tp->tsq_flags);



		sk = (struct sock *)tp;

		if (!sk->sk_lock.owned &&

		    test_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags)) {

			bh_lock_sock(sk);



			if (!sock_owned_by_user(sk)) {

				clear_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);

				tcp_tsq_handler(sk);

		} else {

			/* defer the work to tcp_release_cb() */

			set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);

			}

			bh_unlock_sock(sk);

		}



		clear_bit(TSQ_QUEUED, &tp->tsq_flags);

		sk_free(sk);

	}

}
@@ -884,7 +884,7 @@ void tcp_wfree(struct sk_buff *skb) 
		if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))

			goto out;



		nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED;

		nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED | TCPF_TSQ_DEFERRED;

		nval = cmpxchg(&tp->tsq_flags, oval, nval);

		if (nval != oval)

			continue;
@@ -2229,6 +2229,8 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, 
		    unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))

			break;



		if (test_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags))

			clear_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);

		if (tcp_small_queue_check(sk, skb, 0))

			break;

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