New and changed VMM tunables

VMM adds the following tunables to the system:

FILE_PAGES_MAX

FILE_PAGES_MAX specifies the maximum capacity, in units of PAGES, to cache file contents. In very large memory systems (typically those with more than 4GB of memory) the general purpose memory pool is allowed to grow to a larger size than the file pages cache. Should the general purpose memory pool exceed the file page cache in size, then the excess of general purpose memory can be utilized as process memory, but not as file cache memory. Increasing FILE_PAGES_MAX increases the system's capacity to cache file pages, but decreases its ability to support general purpose memory. Conversely, decreasing FILE_PAGES_MAX decreases the file memory which may be cached, but increases the general purpose memory which can be supported. For example, it is possible to support 64GB of general purpose memory by setting FILE_PAGES_MAX to 262144 (supporting a file system cache of 1 gigabyte of memory).

KMA_POOL_MAX

KMA_POOL_MAX specifies the size (in bytes) of the per-CPU, per-allocation size, memory pool to be retained by the kernel memory allocator. A larger value of KMA_POOL_MAX will increase kernel performance, but at the cost of increased kernel memory consumption.

VMM changes the default value of the following, existing tunable parameter from 30 seconds to 10 seconds:

KMAGBTIME

KMAGBTIME specifies how much time, in seconds, there is between successive attempts by the kernel memory allocator to give back unused memory (for possible use by processes or filesystems). Increasing this value increases the kernel allocator's requirement for memory. Decreasing it increases the CPU usage of the giveback attempts.

Default, minimum, and maximum values for new and changed VMM tunables

Tunable	Default	Minimum	Maximum
KMA_POOL_MAX	Ox10000	0	Ox100000
FILE_PAGES_MAX	980000	32768	16777216
KMAGBTIME	10	5	2400