So, swap is when the computer writes used memory to slow, long term storage because of memory pressure.
Cache is when the OS sticks random bits of files into unused memory to they can be used faster.
Using swap is a sign you need more ram. Using cache is harmless, and the OS will try to fill all free memory with cached files, because worst case scenario there’s no cost.
Using swap isn’t always a sign you need more RAM. Typically, if you use a computer for a while or have a lot of IO operations going on, Linux will decide to swap some things to make more room for cache.
Sometimes Linux just finds that you have a bunch of inactive app memory and it can swap that out to cache way more stuff. That’s just good memory management, but it’s not worth buying more RAM over
That’s totally fair. Most of my “caring about swap” time is when I was managing servers, and so you wouldn’t have inactive apps to get swapped out, thus swap usage was a sign that you needed to get a new server and put down the old one.
Turns out I don’t monitor my home computer the way I monitor the work ones. :)
This. Also most of what you read online about swap is just plain wrong. Tons of people will tell you to reduce swappiness to 1 or just to not use swap at all. It’s crazy how many people have no idea about how it actually works. I do include myself here. I just use a large zram disk so systemd-oom won’t get tripped when 3d rendering. That’s all I need to know.
So, swap is when the computer writes used memory to slow, long term storage because of memory pressure.
Cache is when the OS sticks random bits of files into unused memory to they can be used faster.
Using swap is a sign you need more ram. Using cache is harmless, and the OS will try to fill all free memory with cached files, because worst case scenario there’s no cost.
Using swap isn’t always a sign you need more RAM. Typically, if you use a computer for a while or have a lot of IO operations going on, Linux will decide to swap some things to make more room for cache.
Sometimes Linux just finds that you have a bunch of inactive app memory and it can swap that out to cache way more stuff. That’s just good memory management, but it’s not worth buying more RAM over
That’s totally fair. Most of my “caring about swap” time is when I was managing servers, and so you wouldn’t have inactive apps to get swapped out, thus swap usage was a sign that you needed to get a new server and put down the old one.
Turns out I don’t monitor my home computer the way I monitor the work ones. :)
This. Also most of what you read online about swap is just plain wrong. Tons of people will tell you to reduce swappiness to 1 or just to not use swap at all. It’s crazy how many people have no idea about how it actually works. I do include myself here. I just use a large zram disk so systemd-oom won’t get tripped when 3d rendering. That’s all I need to know.