Tunable Base Page Size

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Figure 1: Kernel memory overhead as a function of base page size
Integrity Virtual Machines Platform Manager
The Integrity Virtual Machines Host, also called the Platform Manager, derives great benefit from
using 64 kB base pages. The Host automatically tunes the base page size appropriately. Under no
circumstances should the base page size for the Integrity Virtual Machines Host be changed to any
value other than 64 kB. Of course, the virtual machine instances, also called the guests, can use
whatever base page size is appropriate for the guest workload.
The primary benefit of large base pages to Integrity Virtual Machines configurations is the reduction in
kernel memory consumption in the Host. Using 64kB base pages in the Host frees up physical
memory that can then be assigned to Guest Virtual Machines.
Working with Tunable Base Page Size
Tuning the base page size
The base page size is tuned by invoking the kctune(1M)command to change the kernel tunable
parameter base_pagesize. The parameter exists on Integrity platforms only; the base page size
cannot be changed from the fixed value of 4 kB on HP 9000 (PA-RISC) platforms.
The base page size is expressed as a value in kilobytes. The value 4 represents a base page size of
4 kB (4096 bytes).
base_pagesize kernel tunable parameter
The default value of the base_pagesize parameter is 4. The Tunable Base Page Size enhancement
has absolutely no effect as long as base_pagesize remains at its default value.
The minimum value to which base_pagesize can be tuned is also 4. It is not possible to adjust the
parameter to a value smaller than the previous fixed default.
The maximum value to which base_pagesize can be tuned is 64. The other permitted values are 8
and 16. Please refer to the base_pagesize(5) manpage for complete details