Optimizing OS Parameters

You can improve the openGauss performance by modifying key parameters of the OS based on actual service requirements during the performance optimization.

Prerequisites

You have checked whether the OS parameters are set to the suggested values using gs_check. If not, modify them as required.

Memory Parameters

In the sysctl.conf file, change the value of vm.extfrag_threshold to 1000 (reference value). If the file does not contain memory parameters, add them manually.

vim /etc/sysctl.conf

Run the following command to make the modification take effect:

sysctl -p

Network Parameters

In the sysctl.conf file, modify network parameters. If the file does not contain such parameters, add them manually. For details, see Table 1.

vim /etc/sysctl.conf

Run the following command to make the modification take effect:

sysctl -p

Table 1 Network parameters

Parameter	Reference Value	Description
net.ipv4.tcp_timestamps	1	Specifies whether to enable quick reclamation of the sockets in TIME-WAIT state during TCP connection establishment. The default value 0 indicates that quick reclamation is disabled, and the value 1 indicates that quick reclamation is enabled.
net.ipv4.tcp_mem	94500000 915000000 927000000	94500000: If less than 94,500,000 pages are used by the TCP, the kernel is not affected. 915000000: If more than 915,000,000 pages are used by the TCP, the kernel enters the memory pressure mode. 927000000: If more than 927,000,000 pages are used by the TCP, the "Out of socket memory." message is displayed.
net.ipv4.tcp_max_orphans	3276800	Maximum number of the orphan sockets
net.ipv4.tcp_fin_timeout	60	Default timeout period
net.ipv4.ip_local_port_range	26000 65535	Port range that can be used by TCP or UDP

Use the ifconfig command to set the maximum transmission unit (MTU) of 10 GE NICs. The value 8192 is recommended because this setting improves the network bandwidth usage.

Example:

#ifconfig ethx mtu 8192
#ifconfig ethx
ethx   Link encap:Ethernet  HWaddr XX:XX:XX:XX:XX:XX
inet addr:xxx.xxx.xxx.xxx  Bcast:xxx.xxx.xxx.xxx  Mask:xxx.xxx.xxx.0
inet6 addr: fxxx::9xxx:bxxx:xxxa:1d18/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:8192  Metric:1
RX packets:179849803 errors:0 dropped:0 overruns:0 frame:0
TX packets:40492292 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:17952090386 (17120.4 Mb)  TX bytes:171359670290 (163421.3 Mb)

NOTE:
ethx indicates the 10 GE service NIC used in the database.
The first command is used to set the MTU. The second command is used to verify that the MTU has been successfully set. The texts in bold indicate the value of the MTU.
Set the MTU as user root.

Use ethtool to set the length of the receiving (RX) queue and that of the sending (TX) queue for 10 GE NICs. The value 4096 is recommended because this setting improves the network bandwidth usage.
Example:
```
# ethtool -G ethx rx 4096 tx 4096
# ethtool -g ethx
Ring parameters for ethx:
Pre-set maximums:
RX:             4096
RX Mini:        0
RX Jumbo:       0
TX:             4096
Current hardware settings:
RX:             4096
RX Mini:        0
RX Jumbo:       0
TX:             4096
```
NOTE:
- ethx indicates the 10 GE service NIC used in the database.
- The first command is used to set the lengths of the receiving and sending queues. The second command is to verify whether the lengths have been successfully set. If information similar to the example is displayed, the setting is successful.
- Set the lengths of the receiving and sending queues as user root.

I/O Parameters

Set the hugepage attribute. Run the following commands to disable the transparent huge page function:

echo never > /sys/kernel/mm/transparent_hugepage/enabled
echo never > /sys/kernel/mm/transparent_hugepage/defrag

Run the following command to make the modification take effect:

reboot