If memory is added to a BDA server, tuning the kernel parameter, vm.min_free_kbytes, is recommended based on: Oracle Linux : Recommended Value of vm.min_free_kbytes Kernel Tuning Parameter (Doc ID 2501269.1). Tuning vm.min_free_kbytes can prevent memory fragmentation issues because it allows the OS to reclaim memory faster.
Additionally on the BDA vm.min_free_kbytes may need to be increased on clusters that are either large or have high network traffic. If this is not done, different symptoms including reduced performance, unexpected reboots and network errors can occur.
Based on the Oracle Linux recommendation vm.min_free_kbytes (KB) should be set using the following calculation:
MAX(1GB * number_numa_nodes, 0.5% * total_memory)
The number of NUMA nodes on the BDA is 2. Hence the default setting for vm.min_free_kbytes on the BDA is 2GB.
To tune vm.min_free_kbytes set the value to (0.5% * total_memory).
Note that when calculating the value the recommendation is to round values to the number of kilobytes representing the nearest gigabyte value. So for example if a vm.min_free_kbytes value is calculated to be ~4GB set it to 4GB i.e. 4194304 KB. If a vm.min_free_kbytes value is calculated to be ~8GB set it to 8GB i.e. 8388608 KB.
