Default setting of memmap-on-memory

7.1 LPAR mode z/VM guest

You can set the memmap-on-memory default value of your Linux® instance by using a kernel parameter.

About this task

Hotplug memory blocks inherit the memmap-on-memory setting from the global parameter. The setting can be specified during configuration (using chmem -c -b -m {0|1}), but only if the kernel parameter memory_hotplug.memmap_on_memory=1 is enabled.

Procedure

To enable global memmap-on-memory settings at boot time, add the following kernel boot command-line parameter:

memory_hotplug.memmap_on_memory=1

The memmap-on-memory setting depends on when the memory blocks were defined:

Memory defined at boot: Memory blocks that are configured online during system boot have memmap-on-memory=0. This is because these blocks are not initially added with memmap-on-memory support. You can change this setting later.
Hotplug memory: Hotplug memory blocks added dynamically during runtime defaults its memmap-on-memory attribute value to the global memmap-on-memory parameter settings.