From 114f39feab360e6c7b0c4238697f223444d662a1 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 2 May 2018 20:25:13 -0700 Subject: [PATCH] tcp: restore autocorking When adding rb-tree for TCP retransmit queue, we inadvertently broke TCP autocorking. tcp_should_autocork() should really check if the rtx queue is not empty. Tested: Before the fix : $ nstat -n;./netperf -H 10.246.7.152 -Cc -- -m 500;nstat | grep AutoCork MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.246.7.152 () port 0 AF_INET Recv Send Send Utilization Service Demand Socket Socket Message Elapsed Send Recv Send Recv Size Size Size Time Throughput local remote local remote bytes bytes bytes secs. 10^6bits/s % S % S us/KB us/KB 540000 262144 500 10.00 2682.85 2.47 1.59 3.618 2.329 TcpExtTCPAutoCorking 33 0.0 // Same test, but forcing TCP_NODELAY $ nstat -n;./netperf -H 10.246.7.152 -Cc -- -D -m 500;nstat | grep AutoCork MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.246.7.152 () port 0 AF_INET : nodelay Recv Send Send Utilization Service Demand Socket Socket Message Elapsed Send Recv Send Recv Size Size Size Time Throughput local remote local remote bytes bytes bytes secs. 10^6bits/s % S % S us/KB us/KB 540000 262144 500 10.00 1408.75 2.44 2.96 6.802 8.259 TcpExtTCPAutoCorking 1 0.0 After the fix : $ nstat -n;./netperf -H 10.246.7.152 -Cc -- -m 500;nstat | grep AutoCork MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.246.7.152 () port 0 AF_INET Recv Send Send Utilization Service Demand Socket Socket Message Elapsed Send Recv Send Recv Size Size Size Time Throughput local remote local remote bytes bytes bytes secs. 10^6bits/s % S % S us/KB us/KB 540000 262144 500 10.00 5472.46 2.45 1.43 1.761 1.027 TcpExtTCPAutoCorking 361293 0.0 // With TCP_NODELAY option $ nstat -n;./netperf -H 10.246.7.152 -Cc -- -D -m 500;nstat | grep AutoCork MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.246.7.152 () port 0 AF_INET : nodelay Recv Send Send Utilization Service Demand Socket Socket Message Elapsed Send Recv Send Recv Size Size Size Time Throughput local remote local remote bytes bytes bytes secs. 10^6bits/s % S % S us/KB us/KB 540000 262144 500 10.00 5454.96 2.46 1.63 1.775 1.174 TcpExtTCPAutoCorking 315448 0.0 Fixes: 75c119afe14f ("tcp: implement rb-tree based retransmit queue") Signed-off-by: Eric Dumazet Reported-by: Michael Wenig Tested-by: Michael Wenig Signed-off-by: Eric Dumazet Reported-by: Michael Wenig Tested-by: Michael Wenig Acked-by: Neal Cardwell Acked-by: Soheil Hassas Yeganeh Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 44be7f43455e..c9d00ef54dec 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -697,7 +697,7 @@ static bool tcp_should_autocork(struct sock *sk, struct sk_buff *skb, { return skb->len < size_goal && sock_net(sk)->ipv4.sysctl_tcp_autocorking && - skb != tcp_write_queue_head(sk) && + !tcp_rtx_queue_empty(sk) && refcount_read(&sk->sk_wmem_alloc) > skb->truesize; }