Invalid argument" setting key "net.core.somaxconn"

Question

I tried setting Linux kernel. After editing /etc/sysctl.conf and executing the sysctl -p
it shows error

Invalid argument" setting key "net.core.somaxconn"

Linux distribution: Ubuntu 12.04.4 LTS, x86_64, 3.2.0-60-generic

$ cat /etc/sysctl.conf
net.ipv4.conf.eth0.arp_notify = 1
vm.swappiness = 0
net.ipv4.tcp_rmem = 4096 87380 4194304
net.ipv4.tcp_wmem = 4096 16384 4194304
net.core.wmem_default = 8388608
net.core.rmem_default = 8388608
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.core.somaxconn = 262144
net.core.netdev_max_backlog = 262144
fs.file-max = 1048576
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 1200
net.ipv4.tcp_max_syn_backlog = 409600
net.ipv4.ip_local_port_range = 1024 65000
net.ipv4.tcp_max_orphans = 262144

Can I increase the net.core.somaxconn to 262144?

Answer 1

Same issue I got into when I tried to fine tune my nginx. This is the problem with the patch that been made to Ubuntu kernel. The

sk_max_ack_backlog field of the sock structure is defined as unsigned short.

Therefore, the backlog argument in inet_listen() shouldn't exceed USHRT_MAX. The backlog argument in the listen() syscall is truncated to the somaxconn value. So, the somaxconn value shouldn't exceed 65535 (USHRT_MAX).

So in short to make your net.core.somaxconn work you should not give value greater then 65535

net.core.somaxconn = 65535

This is sad but we have to live with it until unless you are ok to repatch your kernel: https://lists.ubuntu.com/archives/kernel-team/2013-October/033041.html