posted in Selfhosted

A9nWGzYt@A9nWGzYt@lemmy.dbzer0.com

Why is my home server using so much RAM for cache + buffer?

I have noticed that my home server is strangely using lots of swap (~5 GB), despite having only a few lightweight processes running and loads of RAM installed (32 GB).

Upon configuring Grafana + Prometheus, I noticed a trend where cache + buffer will progressively increase until swap starts to be used. My system and services combined will use ~8 GB RAM. Upon rebooting, the cache + buffer will start anywhere from 3–10 GB, progressively ramp up to ~25 GB in 1–2h, where swap will start to be needed (~3 GB). See the image attached for reference.

My swap filesystem is on an expensive (to me) SSD, and I would like to reduce its wear by as much as possible. I understand that swap can introduce only minimal wear on SSDs depending on its nature and that it can be harmless, but I am still not sure what is causing this behavior (and why) and whether I should worry about it or not. So I figured I should investigate what is happening here.

My main question is, how can I figure out what is causing this behavior? Is it expected? I am looking for guidance from others who are more experienced than me in the topic.

A little bit about my system:

I am running Debian 12 on an NVMe SSD containing the root partition (btrfs) and docker services. I also have two HDDs, one with persistent data (ext4), and the other with backups (ext4). This is majoritarily a single-user machine. I tried using the following kernel parameters, but it hasn’t helped:

vm.swappiness=10
vm.vfs_cache_pressure=200

My docker services are:

  • *arr stack
  • jellyfin
  • nextcloud
  • immich
  • open-webui + ollama
  • pi-hole
  • invidious
  • romm
  • nginx proxy manager
  • grafana + prometheus
  • other minor services that I don’t think are doing much (uptime-kuma, stirlingpdf, vaultwarden, etc)
irmadlad@irmadlad@lemmy.world

Replying to an earlier post

Huh…


  System load:  1.26                Temperature:           57.0 C
  Usage of /:   20.4% of 454.86GB   Processes:             527
  Memory usage: 44%                 Users logged in:       1
  Swap usage:   0%                  IPv4 address for eno1: 192.168.1.190

Ubuntu 22.04.5 - 32 GB RAM - 53 total containers

cat /proc/sys/vm/swappiness: 60 (pretty much default)

cat /proc/pressure/cpu: some avg10=0.68 avg60=0.62 avg300=0.67 total=960097774
full avg10=0.00 avg60=0.00 avg300=0.00 total=0
cat /proc/pressure/memory: some avg10=0.00 avg60=0.00 avg300=0.00 total=0
full avg10=0.00 avg60=0.00 avg300=0.00 total=0
cat /proc/pressure/io: some avg10=1.16 avg60=4.88 avg300=3.85 total=2831425045
full avg10=1.11 avg60=4.54 avg300=3.58 total=2653626377
en
A9nWGzYt@A9nWGzYt@lemmy.dbzer0.com

Replying to an earlier post

Well, here I have 41 containers and:

free -hm
               total        used        free      shared  buff/cache   available
Mem:            31Gi       5.7Gi       426Mi       207Mi        25Gi        25Gi
Swap:           31Gi       3.7Gi        28Gi

As well as

cat /proc/sys/vm/swappiness: 10

and

$ cat /proc/pressure/cpu
some avg10=0.00 avg60=0.00 avg300=0.00 total=302436406
full avg10=0.00 avg60=0.00 avg300=0.00 total=0

$ cat /proc/pressure/memory
some avg10=0.00 avg60=0.00 avg300=0.00 total=64263542
full avg10=0.00 avg60=0.00 avg300=0.00 total=63043120

$ cat /proc/pressure/io
some avg10=1.99 avg60=1.67 avg300=1.61 total=1844790000
full avg10=1.90 avg60=1.59 avg300=1.56 total=1788451770
irmadlad@irmadlad@lemmy.world

Replying to an earlier post

41 containers:

Are you noticing any stalling or stuttering when running apps or using multiple apps? If ‘no’ then I’d agree with the ones that are telling you it’s fine. Dats how Linux do. I’ve always been told to let Linux handle that unless it’s causing problems for you. And even then, after exhausting all other things that may cause this. Now whether that is sage advice, I couldn’t comment to that, however and anecdotally, it’s served me well.