Numa balancer in Linux

Question

Is NUMA balancer enabled by default in recent Linux versions? If so how can I disable the NUMA balancer please let me know.

Answer 1

This depends on which distribution you are on and the underlying hardware. NUMA should be enabled in the BIOS. To check if NUMA is disabled on your linux use:

`grep -i numa /var/log/dmesg` 

this returns No NUMA configuration found, when NUMA enabled, dmesg does not show any information of NUMA initialization.

If NUMA is enabled in BIOS, then execute the command numactl --hardware to list the available nodes on the system.

Note, you can also set numa=off to disable in grub.conf, but its best to change it using BIOS settings.

Answer 2

The automatic NUMA balancing can be disabled by passing the numa_balancing=disable parameter to the kernel. The exact way of doing so depends on the boot loader in use. The same parameter could be controlled via the kernel.numa_balancing sysctl:

echo 0 > /proc/sys/kernel/numa_balancing

or

sysctl -w kernel.numa_balancing=0

It could also be set in /etc/sysctl.conf on distributions that process that file.