Home / server / Questions / 328722
Accepted
John Bachir
Asked: 2011-11-08 18:24:56 +0800 CST

What does monit consider to be memory usage?

  • 772

Once can have monit monitor memory usage…

check system foo
  if memory usage > 95% then alert

Does it use free RAM, or free -/+ buffers/cache? (or something else?)

# free -m
             total       used       free     shared    buffers     cached
Mem:           998        851        146          0        114         70
-/+ buffers/cache:        666        332
Swap:         2047         54       1993
memory memory-usage monit

3 Answers

  1. Best Answer

    This could be get from the source of monit https://github.com/arnaudsj/monit/tree/master/process.

    For linux the value is computed in sysdep_LINUX.c and comes from /proc/meminfo :

    si->total_mem_kbyte = systeminfo.mem_kbyte_max - mem_free - buffers - cached;

    In other words monit use as memory usage MemTotal - MemFree - Buffers - Cached.

    In your case 998 - 146 - 114 - 70 = 668

    • 5

  2. On latest Monit (ie: 5.25.x) the memory usage value accounts for ZFS ARC cache - so if someout is using ZFS, used memory is not ballooned by reclaimable ARC data.

    Current memory usage is calculated as:

    si->memory.usage.bytes = systeminfo.memory.size - zfsarcsize -
(uint64_t)(mem_free + buffers + cached + slabreclaimable) * 1024;

    See here from more details.

    • 0

  3. AFAIK, it based on:

    used memory - cached = 851 - 70 = 781
    • -1