Optimizable Node System Parameters

CCE provides default node system parameters, which may cause performance bottlenecks in some scenarios. Therefore, you can customize and optimize some node system parameters. Optimizable Node System Parameters describes the node system parameters.

The modification has certain risks. Be familiar with Linux commands and Linux OS.
The parameters listed in Table 1 have been tested and verified. Do not modify other parameters. Otherwise, node faults may occur.
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.

**Table 1** System parameters that can be optimized
Parameter	Parameter Location	Description	Reference
kernel.pid_max	/etc/sysctl.conf	Maximum number of process IDs on a node Obtaining the parameter: sysctl kernel.pid_max	Changing Process ID Limits (kernel.pid_max)
RuntimeMaxUse	/etc/systemd/journald.conf	Upper limit of the memory occupied by the node log cache. If this parameter is not set, a large amount of memory will be occupied after the system runs for a long time. Obtaining the parameter: cat /etc/systemd/journald.conf \| grep RuntimeMaxUse	Changing the RuntimeMaxUse of the Memory Used by the Log Cache on a Node
Openfiles	/etc/security/limits.conf	Maximum number of file handles for a single process on a node, which can be adjusted as required. Obtaining the parameter: ulimit -n	Changing the Maximum Number of File Handles for a Single Process on a Node
(inside the Openfiles container) LimitNOFILE LimitNPROC	CentOS/EulerOS: Docker nodes: /usr/lib/systemd/system/docker.service Docker nodes: /usr/lib/systemd/system/containerd.service Ubuntu: Docker nodes: /lib/systemd/system/docker.service Docker nodes: /lib/systemd/system/containerd.service	Maximum number of file handles for a single process in a container, which can be adjusted as required. Obtaining the parameter: Docker nodes: cat /proc/`pidof dockerd`/limits \| grep files containerd nodes: cat /proc/`pidof containerd`/limits \| grep files	Changing the Maximum Number of File Handles for a Single Container Process
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	Changing the Maximum Number of System-Level File Handles on a Node
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] Adjust the buckets value to ensure that the bucket usage is lower than 0.7. Obtaining the parameter: sysctl net.netfilter.nf_conntrack_count sysctl net.netfilter.nf_conntrack_buckets sysctl net.netfilter.nf_conntrack_max	Modifying Node Kernel Parameters
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_be_liberal	/etc/sysctl.conf	The parameter value is 0 or 1. 0: The function is disabled. All RST packets that are not in the TCP window are marked as invalid. 1: The function is enabled. Only RST packets that are not in the TCP window are marked as invalid. In containers, enabling this parameter can prevent the bandwidth of TCP connections that have been translated using NAT from being limited. Obtaining the parameter: sysctl net.netfilter.nf_conntrack_tcp_be_liberal
tcp_keepalive_time	/etc/sysctl.conf	Interval at which a TCP keepalive message is sent. If this parameter is set to a large value, TCP connections may be suspended in the Close_wait phase for a long time, exhausting system resources. Obtaining the parameter: sysctl net.ipv4.tcp_keepalive_time
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
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.core.somaxconn	/etc/sysctl.conf	Maximum number of TCP connections. This parameter controls the number of TCP connections in a queue. If this parameter is set to a small value, the number of TCP connections is prone to insufficiency. If this parameter is set to a large value, system resources may be wasted because each client waiting for connection in the connection queue occupies certain memory resources. Obtaining the parameter: sysctl net.core.somaxconn
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
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
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.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.ipv4.neigh.default.gc_thresh1 net.ipv4.neigh.default.gc_thresh2 net.ipv4.neigh.default.gc_thresh3	/etc/sysctl.conf	Optimization of the garbage collection of ARP entries. gc_thresh1: indicates the minimum number of entries that can be reserved. If the number of entries is less than the gc_thresh1 value, the garbage collector (GC) will not reclaim these entries. Do not modify the default parameter setting. gc_thresh2: When the number of entries exceeds the value of this parameter, the GC will clear the entries that have been stored for more than 5 seconds. Do not modify the default parameter setting. gc_thresh3: indicates the maximum number of non-permanent entries. If the system provides a large number of APIs or is directly connected to a large number of devices, increase the value of this parameter. Obtaining the parameter: sysctl net.ipv4.neigh.default.gc_thresh1 sysctl net.ipv4.neigh.default.gc_thresh2 sysctl net.ipv4.neigh.default.gc_thresh3
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

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