How Windows Updates the LRU (Least Recently Used) List

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows versions 3.0 and 3.1

The following information describes how the LRU (Least Recently Used) list is updated in Windows.

When a function in a code segment is called through its thunk, one instruction in the thunk is to update a record in the EXE header. This is done to notify Windows that a segment has been recently accessed. Windows updates the LRU list periodically according to the records. The routine that does the job searches for segments that have been accessed since the last time the routine was called. When it has been determined that the list needs to be updated, the routine resets its reference byte and puts it at the top of the LRU list. By default, the updating routine is called every four timer ticks from the INT 8 handler.