Check manual page of mem.win


Usage of main memory and page file

Distribution: official part of Check_MK
License: GPL
Supported Agents: Windows

This check measures the current usage of physical RAM and of the commit charge. The "commit charge" was previously confusingly named "pagefile". Please note that Microsoft themselves use this naming in some applications.

Due to how Windows optimizes memory management, physical memory is in practice almost always fully utilized. The Memory usage this check displays says how much memory is actually required by processes, in contrast to caches that could be freed if the need arises.

In the same vein Windows may hold data in RAM and pagefile at the same time or it may hold data in the pagefile even when there is RAM available, when it determines this may improve performance. As a result, the real pagefile usage is not only hard to determine, it's also utterly useless when we want to determine resource usage on the system.

The commit charge instead tells us how much of the memory used in total (RAM + swap) is really required, ignoring overlap and caches. Commit Charge minus Memory Usage is approximately the amount of the pagefile used for "relevant" data, but further optimizations may lead to offsets (to the point where Commit Charge - Memory Usage can be negative).

Item

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Discovery

mem.win creates one check for each host that provides data about the page file. If that information is missing, a Unix-like system is assumed and the check mem.used is being used instead.