diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 3c12d9a7ed00391d5c3f49ef80d7b1ae9abc40fe..12ba2cd9f03d9ca101ccd4d37ebbe928e5334e23 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -156,6 +156,16 @@ tcp_app_win - INTEGER
buffer. Value 0 is special, it means that nothing is reserved.
Default: 31
+tcp_autocorking - BOOLEAN
+ Enable TCP auto corking :
+ When applications do consecutive small write()/sendmsg() system calls,
+ we try to coalesce these small writes as much as possible, to lower
+ total amount of sent packets. This is done if at least one prior
+ packet for the flow is waiting in Qdisc queues or device transmit
+ queue. Applications can still use TCP_CORK for optimal behavior
+ when they know how/when to uncork their sockets.
+ Default : 1
+
tcp_available_congestion_control - STRING
Shows the available congestion control choices that are registered.
More congestion control algorithms may be available as modules,
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 70e55d200610ec6596f7c90715bff4749b462f6e..f7e1ab2139efe7f6208836c1797a2db6fb603749 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -282,6 +282,7 @@ extern int sysctl_tcp_limit_output_bytes;
extern int sysctl_tcp_challenge_ack_limit;
extern unsigned int sysctl_tcp_notsent_lowat;
extern int sysctl_tcp_min_tso_segs;
+extern int sysctl_tcp_autocorking;
extern atomic_long_t tcp_memory_allocated;
extern struct percpu_counter tcp_sockets_allocated;
diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 1bdb4a39d1e1512da2091f1c4e897c5e03527554..bbaba22f2d1bcfa25517acb1bf19fc8eb648c480 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -258,6 +258,7 @@ enum
LINUX_MIB_TCPFASTOPENCOOKIEREQD, /* TCPFastOpenCookieReqd */
LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES, /* TCPSpuriousRtxHostQueues */
LINUX_MIB_BUSYPOLLRXPACKETS, /* BusyPollRxPackets */
+ LINUX_MIB_TCPAUTOCORKING, /* TCPAutoCorking */
__LINUX_MIB_MAX
};
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 4a0335854b89c305442e257057ca560811159df8..8ecd7ad959b4c9a1e29d6cf68501c7ba26f0bdf1 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -279,6 +279,7 @@ static const struct snmp_mib snmp4_net_list[] = {
SNMP_MIB_ITEM("TCPFastOpenCookieReqd", LINUX_MIB_TCPFASTOPENCOOKIEREQD),
SNMP_MIB_ITEM("TCPSpuriousRtxHostQueues", LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES),
SNMP_MIB_ITEM("BusyPollRxPackets", LINUX_MIB_BUSYPOLLRXPACKETS),
+ SNMP_MIB_ITEM("TCPAutoCorking", LINUX_MIB_TCPAUTOCORKING),
SNMP_MIB_SENTINEL
};
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 3d69ec8dac578ee101e2c4b9467b3be83a430ac6..38c8ec90ff680001656f9ab53ee838b85827f9ea 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -732,6 +732,15 @@ static struct ctl_table ipv4_table[] = {
.extra1 = &zero,
.extra2 = &gso_max_segs,
},
+ {
+ .procname = "tcp_autocorking",
+ .data = &sysctl_tcp_autocorking,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &one,
+ },
{
.procname = "udp_mem",
.data = &sysctl_udp_mem,
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c4638e6f023843bedbceb91f1bef3c424ad3b666..0ca87547becbe939c19e93c6f68983c40087da86 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -285,6 +285,8 @@ int sysctl_tcp_fin_timeout __read_mostly = TCP_FIN_TIMEOUT;
int sysctl_tcp_min_tso_segs __read_mostly = 2;
+int sysctl_tcp_autocorking __read_mostly = 1;
+
struct percpu_counter tcp_orphan_count;
EXPORT_SYMBOL_GPL(tcp_orphan_count);
@@ -619,19 +621,52 @@ static inline void tcp_mark_urg(struct tcp_sock *tp, int flags)
tp->snd_up = tp->write_seq;
}
-static inline void tcp_push(struct sock *sk, int flags, int mss_now,
- int nonagle)
+/* If a not yet filled skb is pushed, do not send it if
+ * we have packets in Qdisc or NIC queues :
+ * Because TX completion will happen shortly, it gives a chance
+ * to coalesce future sendmsg() payload into this skb, without
+ * need for a timer, and with no latency trade off.
+ * As packets containing data payload have a bigger truesize
+ * than pure acks (dataless) packets, the last check prevents
+ * autocorking if we only have an ACK in Qdisc/NIC queues.
+ */
+static bool tcp_should_autocork(struct sock *sk, struct sk_buff *skb,
+ int size_goal)
{
- if (tcp_send_head(sk)) {
- struct tcp_sock *tp = tcp_sk(sk);
+ return skb->len < size_goal &&
+ sysctl_tcp_autocorking &&
+ atomic_read(&sk->sk_wmem_alloc) > skb->truesize;
+}
+
+static void tcp_push(struct sock *sk, int flags, int mss_now,
+ int nonagle, int size_goal)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
- if (!(flags & MSG_MORE) || forced_push(tp))
- tcp_mark_push(tp, tcp_write_queue_tail(sk));
+ if (!tcp_send_head(sk))
+ return;
+
+ skb = tcp_write_queue_tail(sk);
+ if (!(flags & MSG_MORE) || forced_push(tp))
+ tcp_mark_push(tp, skb);
+
+ tcp_mark_urg(tp, flags);
+
+ if (tcp_should_autocork(sk, skb, size_goal)) {
- tcp_mark_urg(tp, flags);
- __tcp_push_pending_frames(sk, mss_now,
- (flags & MSG_MORE) ? TCP_NAGLE_CORK : nonagle);
+ /* avoid atomic op if TSQ_THROTTLED bit is already set */
+ if (!test_bit(TSQ_THROTTLED, &tp->tsq_flags)) {
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAUTOCORKING);
+ set_bit(TSQ_THROTTLED, &tp->tsq_flags);
+ }
+ return;
}
+
+ if (flags & MSG_MORE)
+ nonagle = TCP_NAGLE_CORK;
+
+ __tcp_push_pending_frames(sk, mss_now, nonagle);
}
static int tcp_splice_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
@@ -934,7 +969,8 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
wait_for_sndbuf:
set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
wait_for_memory:
- tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH);
+ tcp_push(sk, flags & ~MSG_MORE, mss_now,
+ TCP_NAGLE_PUSH, size_goal);
if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
goto do_error;
@@ -944,7 +980,7 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
out:
if (copied && !(flags & MSG_SENDPAGE_NOTLAST))
- tcp_push(sk, flags, mss_now, tp->nonagle);
+ tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
return copied;
do_error:
@@ -1225,7 +1261,8 @@ int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
wait_for_memory:
if (copied)
- tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH);
+ tcp_push(sk, flags & ~MSG_MORE, mss_now,
+ TCP_NAGLE_PUSH, size_goal);
if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
goto do_error;
@@ -1236,7 +1273,7 @@ int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
out:
if (copied)
- tcp_push(sk, flags, mss_now, tp->nonagle);
+ tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
release_sock(sk);
return copied + copied_syn;