diff options
| author | Eric Dumazet <edumazet@google.com> | 2018-04-16 10:33:37 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-04-16 18:26:37 -0400 |
| commit | 03f45c883c6f391ed4fff8292415b35bd1107519 (patch) | |
| tree | 826d80967d0b56f08e19072b7fa5810aa03ca667 /net/ipv4 | |
| parent | 796f82eafcd96629c2f9a0332dbb4f474854aaf8 (diff) | |
| download | linux-03f45c883c6f391ed4fff8292415b35bd1107519.tar.bz2 | |
tcp: avoid extra wakeups for SO_RCVLOWAT users
SO_RCVLOWAT is properly handled in tcp_poll(), so that POLLIN is only
generated when enough bytes are available in receive queue, after
David change (commit c7004482e8dc "tcp: Respect SO_RCVLOWAT in tcp_poll().")
But TCP still calls sk->sk_data_ready() for each chunk added in receive
queue, meaning thread is awaken, and goes back to sleep shortly after.
Tested:
tcp_mmap test program, receiving 32768 MB of data with SO_RCVLOWAT set to 512KB
-> Should get ~2 wakeups (c-switches) per MB, regardless of how many
(tiny or big) packets were received.
High speed (mostly full size GRO packets)
received 32768 MB (100 % mmap'ed) in 8.03112 s, 34.2266 Gbit,
cpu usage user:0.037 sys:1.404, 43.9758 usec per MB, 65497 c-switches
received 32768 MB (99.9954 % mmap'ed) in 7.98453 s, 34.4263 Gbit,
cpu usage user:0.03 sys:1.422, 44.3115 usec per MB, 65485 c-switches
Low speed (sender is ratelimited and sends 1-MSS at a time, so GRO is not helping)
received 22474.5 MB (100 % mmap'ed) in 6015.35 s, 0.0313414 Gbit,
cpu usage user:0.05 sys:1.586, 72.7952 usec per MB, 44950 c-switches
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/tcp.c | 4 | ||||
| -rw-r--r-- | net/ipv4/tcp_input.c | 15 |
2 files changed, 17 insertions, 2 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 0abd8d1d3d1d..c768d306b657 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1705,6 +1705,10 @@ EXPORT_SYMBOL(tcp_peek_len); int tcp_set_rcvlowat(struct sock *sk, int val) { sk->sk_rcvlowat = val ? : 1; + + /* Check if we need to signal EPOLLIN right now */ + tcp_data_ready(sk); + if (sk->sk_userlocks & SOCK_RCVBUF_LOCK) return 0; diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index d854363a4387..f93687f97d80 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4576,6 +4576,17 @@ err: } +void tcp_data_ready(struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + int avail = tp->rcv_nxt - tp->copied_seq; + + if (avail < sk->sk_rcvlowat && !sock_flag(sk, SOCK_DONE)) + return; + + sk->sk_data_ready(sk); +} + static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) { struct tcp_sock *tp = tcp_sk(sk); @@ -4633,7 +4644,7 @@ queue_and_out: if (eaten > 0) kfree_skb_partial(skb, fragstolen); if (!sock_flag(sk, SOCK_DEAD)) - sk->sk_data_ready(sk); + tcp_data_ready(sk); return; } @@ -5434,7 +5445,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb, no_ack: if (eaten) kfree_skb_partial(skb, fragstolen); - sk->sk_data_ready(sk); + tcp_data_ready(sk); return; } } |