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| author | Eric Dumazet <edumazet@google.com> | 2012-04-22 23:38:54 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-04-23 22:28:28 -0400 |
| commit | da882c1f2ecadb0ed582628ec1585e36b137c0f0 (patch) | |
| tree | c89b136ec4ae978adf1078fdce199423a59ba8c0 /net | |
| parent | f545a38f74584cc7424cb74f792a00c6d2589485 (diff) | |
| download | linux-da882c1f2ecadb0ed582628ec1585e36b137c0f0.tar.gz linux-da882c1f2ecadb0ed582628ec1585e36b137c0f0.tar.bz2 linux-da882c1f2ecadb0ed582628ec1585e36b137c0f0.zip | |
tcp: sk_add_backlog() is too agressive for TCP
While investigating TCP performance problems on 10Gb+ links, we found a
tcp sender was dropping lot of incoming ACKS because of sk_rcvbuf limit
in sk_add_backlog(), especially if receiver doesnt use GRO/LRO and sends
one ACK every two MSS segments.
A sender usually tweaks sk_sndbuf, but sk_rcvbuf stays at its default
value (87380), allowing a too small backlog.
A TCP ACK, even being small, can consume nearly same truesize space than
outgoing packets. Using sk_rcvbuf + sk_sndbuf as a limit makes sense and
is fast to compute.
Performance results on netperf, single flow, receiver with disabled
GRO/LRO : 7500 Mbits instead of 6050 Mbits, no more TCPBacklogDrop
increments at sender.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Maciej Żenczykowski <maze@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Cc: Rick Jones <rick.jones2@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/tcp_ipv4.c | 3 | ||||
| -rw-r--r-- | net/ipv6/tcp_ipv6.c | 3 |
2 files changed, 4 insertions, 2 deletions
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 917607e9bd5b..cf97e9821d76 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1752,7 +1752,8 @@ process: if (!tcp_prequeue(sk, skb)) ret = tcp_v4_do_rcv(sk, skb); } - } else if (unlikely(sk_add_backlog(sk, skb, sk->sk_rcvbuf))) { + } else if (unlikely(sk_add_backlog(sk, skb, + sk->sk_rcvbuf + sk->sk_sndbuf))) { bh_unlock_sock(sk); NET_INC_STATS_BH(net, LINUX_MIB_TCPBACKLOGDROP); goto discard_and_relse; diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index b04e6d8a8371..5fb19d345cfd 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1654,7 +1654,8 @@ process: if (!tcp_prequeue(sk, skb)) ret = tcp_v6_do_rcv(sk, skb); } - } else if (unlikely(sk_add_backlog(sk, skb, sk->sk_rcvbuf))) { + } else if (unlikely(sk_add_backlog(sk, skb, + sk->sk_rcvbuf + sk->sk_sndbuf))) { bh_unlock_sock(sk); NET_INC_STATS_BH(net, LINUX_MIB_TCPBACKLOGDROP); goto discard_and_relse; |