[PATCH net-next] tcp: Remove tcp_low_latency sysctl.

[PATCH net-next] tcp: Remove tcp_low_latency sysctl.

[Tonghao Zhang]

The prequeue has been removed from the kernel. If we leave
the tcp_low_latency in kernel, it may confuse the users.
If users can't find the option, the doc may tell them why.
So we remove also the sysctl about tcp_low_latency.

Signed-off-by: Tonghao Zhang <zhangtonghao@didichuxing.com>
---
 Documentation/networking/ip-sysctl.txt |  2 +-
 net/ipv4/sysctl_net_ipv4.c             | 10 ----------
 2 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 77f4de59dc9c..ac35f5b59739 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -356,7 +356,7 @@ tcp_l3mdev_accept - BOOLEAN
 	compiled with CONFIG_NET_L3_MASTER_DEV.
 
 tcp_low_latency - BOOLEAN
-	This is a legacy option, it has no effect anymore.
+	This is an obsolete option, it has been removed from kernel.
 
 tcp_max_orphans - INTEGER
 	Maximal number of TCP sockets not attached to any user file handle,
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 4602af6d5358..dfebbfcccb87 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -45,9 +45,6 @@ static int tcp_syn_retries_max = MAX_TCP_SYNCNT;
 static int ip_ping_group_range_min[] = { 0, 0 };
 static int ip_ping_group_range_max[] = { GID_T_MAX, GID_T_MAX };
 
-/* obsolete */
-static int sysctl_tcp_low_latency __read_mostly;
-
 /* Update system visible IP port range */
 static void set_local_port_range(struct net *net, int range[2])
 {
@@ -438,13 +435,6 @@ static struct ctl_table ipv4_table[] = {
 		.extra1		= &one,
 	},
 	{
-		.procname	= "tcp_low_latency",
-		.data		= &sysctl_tcp_low_latency,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec
-	},
-	{
 		.procname	= "tcp_congestion_control",
 		.mode		= 0644,
 		.maxlen		= TCP_CA_NAME_MAX,
-- 
2.13.6

Re: [PATCH net-next] tcp: Remove tcp_low_latency sysctl.

[David Miller]

From: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Date: Tue, 12 Dec 2017 06:43:08 -0800

> The prequeue has been removed from the kernel. If we leave
> the tcp_low_latency in kernel, it may confuse the users.
> If users can't find the option, the doc may tell them why.
> So we remove also the sysctl about tcp_low_latency.
> 
> Signed-off-by: Tonghao Zhang <zhangtonghao@didichuxing.com>

If you remove the sysctl, it will break scripts.

That's why we left it around.