linux-monitor

• overview
• memory
  • check memory stat (free)
  • check memory stat with details (htop)
  • check zfs arc (arc_summary)
  • modify zfs config file
  • QA: why memory usage does not add up with processes

overview

• How To Monitor Your CPU and RAM in Linux | Tom's Hardware

memory

check memory stat (free)

➜  ~ free -g
              total        used        free      shared  buff/cache   available
Mem:            108          78           7           0          21          28
Swap:            15           0          15

check memory stat with details (htop)

If we look at htop memory usage carefully, we may find that the memory usage doesn't add up to the processes.

It is mainly because zfs uses 50% (default) of memory as cache.

see:

• ubuntu - htop memory usage does not add up with process list - Super User
• ram - Is ZFS on Ubuntu 20.04 using a ton of memory? - Ask Ubuntu

check zfs arc (arc_summary)

see: - ram - Is ZFS on Ubuntu 20.04 using a ton of memory? - Ask Ubuntu

$ arc_summary

------------------------------------------------------------------------
ZFS Subsystem Report                Thu Sep 08 22:56:19 2022
ARC Summary: (HEALTHY)
    Memory Throttle Count:          0

ARC Misc:
    Deleted:                97.48m
    Mutex Misses:               13.77k
    Evict Skips:                4.02m

ARC Size:               88.42%  47.82   GiB
    Target Size: (Adaptive)     88.48%  47.85   GiB
    Min Size (Hard Limit):      6.25%   3.38    GiB
    Max Size (High Water):      16:1    54.08   GiB

modify zfs config file

sudo vim /etc/modprobe.d/zfs.conf

QA: why memory usage does not add up with processes

see: check memory stat with details (htop)