Overview Mem Info

The Overview Mem Info screen presents the status of various aspects of virtual memory.

Each process running in a CPU consumes both physical and virtual memory. Virtual memory is the underlying disk space made available via NSKCOM to each CPU. A "rule of thumb", a CPU has allocated 2.5 times the amount of virtual memory than physical memory.

Physical memory is the memory actually present in the CPU. For example, you have a 32 Gigabyte processor.

Not all memory is available for virtual use. When memory is locked, it is not allowed to swap to disk. A certain amount of memory is always locked by the operating system at start up. This amount varies as processes start and stop.

Misc. Memory is a 'catch area' for other useful memory counters.

Unsponsored memory is memory that is temporarily not owned by any process but must remain allocated.

Memory pressure is a value from 0 to 7 where 0 is low. It is an indicator of the demand for memory. Systems with plenty of memory have a pressure of 0.

A page fault is the situation where a memory page is needed but not present. This occurs when a process is first started and continues until all needed memory is accessed at least once. Additionally, a page fault can occur when memory that was previously accessed is no longer present, perhaps due to another process needing memory.

Memory Queue is an indication of the number of processes waiting for memory. Newer systems do not seem to have a general memory queue. The servicing of page faults is now handled within the context of a user process (via system code in the background). On older machines, a memory queue was a second ready list because a process must first have memory accessible before it can wait to execute.