During a VMware healthcheck at one of my customers I ran across the following error in /var/log/vmkwarning: “Memory is incorrectly balanced between the NUMA nodes of this system which will lead to poor performance. See /proc/vmware/NUMA/hardware for details on your current memory configuration.”
With the “more” command you can check how the memory is divided over the NUMA Nodes.
Output will look similar to this:
System type : Unspecific System
# NUMA Nodes : 2
Node ID MachineMem ManagedMem CPUs
0 01 8192 MB 7711 MB 0 1
1 02 4096 MB 4037 MB 2 3
The system was setup with 2 x 4GB and 2 x 2GB which results in this error. You can resolve this by changing the 2 x 2GB for 2 x 4GB, or you can disable NUMA in the BIOS. But I would prefer adding the correct size of memory. You would want to fix this because of the fact that when a processor needs more memory it will resort to non-local memory, in other words memory that was assigned to another processor. When using non-local memory data is transferred over the NUMA interconnect which is definitely slower than local memory.