Real memory management in Virtual Memory Manager

In AIX®, virtual-memory segments are partitioned into 4096-byte units called pages. Real memory is divided into 4096-byte page frames.

The VMM has two major functions:

• Manage the allocation of page frames
• Resolve references to virtual-memory pages that are not currently in RAM (stored in paging space) or do not yet exist.

To accomplish these functions, the VMM maintains a free list of available page frames. The VMM also uses a page-replacement algorithm to determine which virtual-memory pages currently in RAM will have their page frames reassigned to the free list. The page-replacement algorithm takes into account the existence of persistent versus working segments, repaging, and VMM thresholds.