From b223feb9de2a65c533ff95c08e834fa732906ea5 Mon Sep 17 00:00:00 2001 From: Eric Dumazet <edumazet@google.com> Date: Sat, 3 Dec 2016 11:14:52 -0800 Subject: [PATCH 03/10] 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: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> --- net/ipv4/tcp_output.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -772,19 +772,19 @@ static void tcp_tasklet_func(unsigned lo 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; - bh_lock_sock(sk); - - if (!sock_owned_by_user(sk)) { - tcp_tsq_handler(sk); - } else { - /* defer the work to tcp_release_cb() */ - set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags); + 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); + } + bh_unlock_sock(sk); } - bh_unlock_sock(sk); - clear_bit(TSQ_QUEUED, &tp->tsq_flags); sk_free(sk); } } @@ -889,7 +889,7 @@ 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; @@ -2222,6 +2222,8 @@ static bool tcp_write_xmit(struct sock * 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;