this post was submitted on 19 Jan 2026
23 points (92.6% liked)

Selfhosted

60587 readers
2023 users here now

A place to share alternatives to popular online services that can be self-hosted without giving up privacy or locking you into a service you don't control.

Rules:

Detailed Rules Post

  1. Be civil.

  2. No spam.

  3. Posts are to be related to self-hosting.

  4. Don't duplicate the full text of your blog or readme if you're providing a link.

  5. Submission headline should match the article title.

  6. No trolling.

  7. Promotion posts require active participation, with an account that is at least 30 days old. F/LOSS without a paywall has exceptions, with requirements. See the rules link for details. Tags [CBH] or [AIP] are required, see the links in Rule 8 for details.

  8. AI-related discussions and AI-involved promotional posts have additional requirements for tagging, as noted in Rule 7 and the AI & Promotional Post Expanded Rules post, and find example disclosures here.

Resources:

Any issues on the community? Report it using the report flag.

Questions? DM the mods!

founded 3 years ago
MODERATORS
ruud@lemmy.world
Loki@lemmy.world
CannaVet@lemmy.world
devve@lemmy.world
ayyy@sh.itjust.works
curbstickle@anarchist.nexus
curbstickle_lw@lemmy.world
23
Help with understanding memory usage discrepancy (lemmy.world)
submitted 5 months ago* (last edited 5 months ago) by a_fancy_kiwi@lemmy.world to c/selfhosted@lemmy.world
34 comments fedilink hide all child comments
 

I recently noticed that htop displays a much lower 'memory in use' number than free -h, top, or fastfetch on my Ubuntu 25.04 server.

I am using ZFS on this server and I've read that ZFS will use a lot of RAM. I also read a forum where someone commented that htop doesn't show caching used by the kernel but I'm not sure how to confirm ZFS is what's causing the discrepancy.

I'm also running a bunch of docker containers and am concerned about stability since I don't know what number I should be looking at. I either have a usable ~22GB of available memory left, ~4GB, or ~1GB depending on what tool I'm using. Is htop the better metric to use when my concern is available memory for new docker containers or are the other tools better?

Server Memory Usage:

  • htop = 8.35G / 30.6G
  • free -h =
               total        used        free      shared  buff/cache   available
Mem:            30Gi        26Gi       1.3Gi       730Mi       4.2Gi       4.0Gi
  • top = MiB Mem : 31317.8 total, 1241.8 free, 27297.2 used, 4355.9 buff/cache
  • fastfetch = 26.54GiB / 30.6GiB

EDIT:

Answer

My Results

tldr: all the tools are showing correct numbers. Htop seems to be ignoring ZFS cache. For the purposes of ensuring there is enough RAM for more docker containers in the future, htop seems to be the tool that shows the most useful number with my setup.

you are viewing a single comment's thread
view the rest of the comments
[–] a_fancy_kiwi@lemmy.world 1 points 5 months ago* (last edited 5 months ago)

Assuming the info in this link is correct, ZFS is using ~20GB for caching which makes htop's ~8GB of in use memory make sense when compared with the results from cat /proc/meminfo. This is great news.

My results after running cat /proc/spl/kstat/zfs/arcstats:

c                               4    19268150979
c_min                           4    1026222848
c_max                           4    31765389312
size                            4    19251112856