1 title: Detailed usage of RAM, Swap, VMalloc and other memory areas on Linux
7 This check measures all of the available memory readings of the complex
8 Linux memory management, which are found in {/proc/meminfo}. You can
9 define levels on every useful value, not only on RAM and Swap. Please
10 note that the Linux memory management is very complex. This check takes
11 all this into account and also correctly handles the concept of
12 caching and the fact that Linux swaps out inactive parts of processes
13 even if there is enough RAM left.
15 This is not a bug, it's a feature. In fact it is the only way to do it right
16 (at least for Linux): What parts of a process currently reside in physical
17 RAM and what parts are swapped out is not related in a direct way with the
20 Linux tends to swap out parts of processes even if RAM is available. It
21 does this in situations where disk buffers (are assumed to) speed up the
22 overall performance more than keeping rarely used parts of processes in RAM.
24 For example after a complete backup of your system you might experiance
25 that your swap usage has increased while you have more RAM free then
26 before. That is because Linux has taken RAM from processes in order to
27 increase disk buffers.
30 Per default the check status is either {OK} in case no RAM is corrupted or
31 {CRIT} in case at least 1 Byte of RAM is corrupted. It is possible to
32 change this behaviour by configuring the warning and critical levels in WATO
33 group {OS} rule {Memory and Swap usage on Linux}. In case the parameter
34 {Upper levels for Hardware Corrupted} is configured with {Absolute levels} or
35 with {Percentual levels} the corresponding levels are considered to generate
36 check status {WARN} or {CRIT}. In case the parameter is configured to
37 {Do not impose levels} the check status is always {OK} independent of a
38 possible RAM corruption.
44 One item per Linux host is being created.