Modifying Kernel Parameters

Purpose

Modify kernel parameters of the operating system to improve server performance.

Procedure

1. Open the sysctl.conf file:

   1	vim /etc/sysctl.conf

2. Press i to enter the insert mode, and add the following kernel parameter settings to the file:

   1 2 3 4 5 6 7 8 9 10

   net.ipv4.tcp_tw_reuse = 1 net.ipv4.tcp_keepalive_time = 60 net.ipv4.tcp_fin_timeout = 1 net.ipv4.tcp_max_tw_buckets = 5000 net.ipv4.ip_local_port_range = 1024 65500 net.core.somaxconn = 65535 net.ipv4.tcp_max_syn_backlog = 262144 net.core.netdev_max_backlog = 262144 net.core.rmem_max = 16777216 net.core.wmem_max = 16777216

   Table 1 describes the kernel parameters.

   Table 1 Kernel parameter description

   Linux Kernel Parameter	Description	Current Value	Default Value
   net.ipv4.tcp_tw_reuse	TIME-WAIT sockets can be reused for new TCP connections. The value 1 indicates enabled, while the value 0 indicates disabled.	1	0
   net.ipv4.tcp_keepalive_time	Specifies the interval (in seconds), at which a keepalive message is sent. This message checks whether a TCP connection is valid.	60	7200
   net.ipv4.tcp_fin_timeout	Specifies the maximum duration for the socket to remain in FIN_WAIT_2 state.	1	60
   net.ipv4.tcp_max_tw_buckets	Specifies the maximum number of TIME_WAIT connections. Reducing the number of TIME_WAIT connections can prevent excessive TIME_WAIT connections from occupying network resources and reduce the latency.	5000	262144
   net.ipv4.ip_local_port_range	Specifies the range of the ports that can be used. Increasing the number of available ports can prevent performance dip when ports are occupied by a large number of connections.	1024 65500	32768 61000
   net.core.somaxconn	Specifies the maximum length of the listening queue for each port in the OS. This parameter applies globally.	65535	128
   net.ipv4.tcp_max_syn_backlog	Specifies the SYN queue length. More network connections can be supported by increasing the queue length.	262144	1024
   net.core.netdev_max_backlog	Specifies the maximum number of data packets that can be sent to the queue when the packet receive rate at each network port is higher than the data packet processing rate of the kernel.	262144	1000
   net.core.rmem_max	Specifies the maximum read buffer of the OS socket.	16777216	131071
   net.core.wmem_max	Specifies the maximum write buffer of the OS socket. Increasing the buffer size can prevent buffer overflow caused by a large number of new connections.	16777216	131071
   net.netfilter.nf_conntrack_max	Specifies the maximum number of connection tracking entries.	0	65536

   

   When a container is used, the nf_conntrack module cannot be disabled. In this case, you need to add kernel parameter settings related to nf_conntrack to the /etc/sysctl.conf file to prevent packet loss caused by full table records.

   1	net.netfilter.nf_conntrack_max=0

3. Press Esc, type :wq!, and press Enter to save the file and exit.
4. Make the configuration take effect.

   1	/sbin/sysctl -p