Modifying Node Kernel Parameters
The default Linux kernel parameters may not satisfy all users. You can modify the /etc/sysctl.conf configuration file on the node to modify the kernel parameters.
- The commands for modifying node system parameters are valid only when public images are used. The commands provided in this document are for reference only when private images are used.
- After the node is restarted, run the sysctl -p command to update the parameter value.
Parameter |
Parameter Location |
Description |
Recommended Value |
---|---|---|---|
file-max |
/etc/sysctl.conf |
Maximum number of file handles in the system, which can be adjusted as required. Obtaining the parameter: sysctl fs.file-max |
fs.file-max=1048576 |
nf_conntrack_buckets nf_conntrack_max |
/etc/sysctl.conf |
Capacity of the connection tracing table, which can be adjusted as required. Bucket usage = [nf_conntrack_count]/[nf_conntrack_buckets] If the CPU usage is greater than 0.7 for a long time, increase the value of buckets to lower the CPU usage to less than 0.7. Obtaining the parameter: sysctl net.netfilter.nf_conntrack_count sysctl net.netfilter.nf_conntrack_buckets sysctl net.netfilter.nf_conntrack_max
NOTE:
Note: net.netfilter.nf_conntrack_buckets on EulerOS 2.3, EulerOS 2.5, and CentOS 7.6 cannot be modified by editing /etc/sysctl.conf, you can modify buckets by modifying /sys/module/nf_conntrack/parameters/hashsize. |
The default value is set based on the node memory size. To change the value, refer to the following formula:
|
net.netfilter.nf_conntrack_tcp_timeout_close |
/etc/sysctl.conf |
Expiration time of the entry of the connection in the close state in the connection tracking table. Shortening the expiration time can speed up the recycling. Obtaining the parameter: sysctl net.netfilter.nf_conntrack_tcp_timeout_close |
net.netfilter.nf_conntrack_tcp_timeout_close=3 |
net.netfilter.nf_conntrack_tcp_be_liberal |
/etc/sysctl.conf |
The parameter value is 0 or 1.
Obtaining the parameter: sysctl net.netfilter.nf_conntrack_tcp_be_liberal |
net.netfilter.nf_conntrack_tcp_be_liberal=1 |
tcp_keepalive_time |
/etc/sysctl.conf |
Interval for sending keepalive detection messages through TCP. If this parameter is set to a large value, TCP connections may be suspended in the Close_wait phase for a long time, which exhausts system resources. Obtaining the parameter: sysctl net.ipv4.tcp_keepalive_time |
net.ipv4.tcp_keepalive_time=600 |
tcp_max_syn_backlog |
/etc/sysctl.conf |
Maximum number of TCP half-connections, that is, the maximum number of connections in the SYN_RECV queue. Obtaining the parameter: sysctl net.ipv4.tcp_max_syn_backlog |
net.ipv4.tcp_max_syn_backlog=8096 |
tcp_max_tw_buckets |
/etc/sysctl.conf |
Specifies the maximum number of sockets in the time-wait state that can exist at any time. If the parameter value is too large, node resources may be exhausted. Obtaining the parameter: sysctl net.ipv4.tcp_max_tw_buckets |
net.ipv4.tcp_max_tw_buckets=5000 |
net.core.somaxconn |
/etc/sysctl.conf |
Maximum number of TCP connections and maximum size of the ESTABLISHED queue. If the parameter value is too small, the value may be insufficient. Obtaining the parameter: sysctl net.core.somaxconn |
net.core.somaxconn=32768 |
max_user_instances |
/etc/sysctl.conf |
Maximum number of inotify instances allowed for each user. If the parameter value is too small, the number of inotify instances may be insufficient in containers. Obtaining the parameter: sysctl fs.inotify.max_user_instances |
fs.inotify.max_user_instances=8192 |
max_user_watches |
/etc/sysctl.conf |
Maximum number of directories of all monitoring instances. If the parameter value is too small, the number of directories may be insufficient in containers. Obtaining the parameter: sysctl fs.inotify.max_user_watches |
fs.inotify.max_user_watches=524288 |
netdev_max_backlog |
/etc/sysctl.conf |
Size of the packet receiving queue of the network protocol stack. If the parameter value is too small, the queue size may be insufficient. Obtaining the parameter: sysctl net.core.netdev_max_backlog |
net.core.netdev_max_backlog=16384 |
net.core.wmem_max net.core.rmem_max |
/etc/sysctl.conf |
Memory size (bytes) of the sending and receiving buffer. If this parameter is set to a small value, the memory size may be insufficient in large file scenarios. Obtaining the parameter: sysctl net.core.wmem_max sysctl net.core.rmem_max |
net.core.wmem_max=16777216 net.core.rmem_max=16777216 |
net.ipv4.neigh.default.gc_thresh1 net.ipv4.neigh.default.gc_thresh2 net.ipv4.neigh.default.gc_thresh3 |
/etc/sysctl.conf |
Garbage collection optimization of ARP entries.
Obtaining the parameter: sysctl net.ipv4.neigh.default.gc_thresh1 sysctl net.ipv4.neigh.default.gc_thresh2 sysctl net.ipv4.neigh.default.gc_thresh3 |
net.ipv4.neigh.default.gc_thresh1=0 net.ipv4.neigh.default.gc_thresh2=4096 net.ipv4.neigh.default.gc_thresh3=163790 |
vm.max_map_count |
/etc/sysctl.conf |
If this parameter is set to a small value, a message is displayed indicating that the space is insufficient during ELK installation. Obtaining the parameter: sysctl vm.max_map_count |
vm.max_map_count=262144 |
Modifying Node Kernel Parameters
Table 1 lists the kernel parameters of nodes. The following describes how to change the value of tcp_keepalive_time, which indicates the interval for sending keepalive detection messages over TCP.
- Log in to the node and check the /etc/sysctl.conf file.
cat /etc/sysctl.conf
- Modify the net.ipv4.tcp_keepalive_time parameter. net.ipv4.tcp_keepalive_time=600 indicates the kernel parameter name and recommended value. For details about the recommended value, see Table 1.
To modify other kernel parameters, replace the parameter names and values in the commands by referring to Table 1.
- If net.ipv4.tcp_keepalive_time has been set in the sysctl.conf file, run the following command to change the value:
sed -i "s/net.ipv4.tcp_keepalive_time=[0-9]*$/net.ipv4.tcp_keepalive_time=600/g" /etc/sysctl.conf && sysctl -p
- If net.ipv4.tcp_keepalive_time is not set in the sysctl.conf file, run the following command to add it:
echo net.ipv4.tcp_keepalive_time=600 >> /etc/sysctl.conf && sysctl -p
- If net.ipv4.tcp_keepalive_time has been set in the sysctl.conf file, run the following command to change the value:
- Run the command in Table 1 to check whether the modification is successful. If the returned value is the same as the modified value, the modification is successful.
# sysctl net.ipv4.tcp_keepalive_time net.ipv4.tcp_keepalive_time = 600
Automatically Configuring Kernel Parameters When Creating a Node or Node Pool
You can set the script to be executed after a node or node pool is created. When creating a node or node pool, you can use the script to configure kernel parameters.
The tcp_keepalive_time parameter is used as an example to describe how to change the interval for sending keepalive detection messages over TCP. The value is the recommended value in Table 1.
- Confirm the OS of the node or node pool to be created, for example, CentOS 7.6.
- Manually test the script commands on nodes in the same cluster and running the same OS. For details about how to manually run the script, see Modifying Node Kernel Parameters.
- When creating a node or node pool, choose Advanced Settings > Post-installation Command to add commands. (The following commands must be configured after the verification is successful.) To modify other kernel parameters, replace the parameter names and values in the commands by referring to Table 1.
- Log in to the node and check the /etc/sysctl.conf file. If net.ipv4.tcp_keepalive_time has been set in the file, run the following command to change it:
sed -i "s/net.ipv4.tcp_keepalive_time=[0-9]*$/net.ipv4.tcp_keepalive_time=600/g" /etc/sysctl.conf && sysctl -p
- Log in to the node and check the /etc/sysctl.conf file. If net.ipv4.tcp_keepalive_time is not set in the file, run the following command to add it:
echo net.ipv4.tcp_keepalive_time=600 >> /etc/sysctl.conf && sysctl -p
The command in the following figure is used only as an example. Change it as required.
- Log in to the node and check the /etc/sysctl.conf file. If net.ipv4.tcp_keepalive_time has been set in the file, run the following command to change it:
- After the node is created, log in to the node and run the command in Table 1 to check whether the modification is successful.
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