Cached memory?

[andyjayh]

I currently have 12Gb ram in my system (6.4.1) and in the system stats dashboard it shows that most of the memory is cached, approx. 10Gb with 1.5Gb used leaving about 600Mb free. Just wanting to understand the cached memory, is this apps and system running in memory and therefore a good thing? The system is fairly idle right now and I have 5 Dockers running but not really active, Plex, Plexpy, Sonarr, Radarr, NZBGet. Should I look at increasing RAM? Any benefit from an additional 4Gb to increase the free RAM?

[pwm]

Cached RAM just means that the OS will keep recently used file data in memory in case some program will request the same data again.

 

The OS always strives to use as much of the available (but unused) RAM for cache so as not to waste excess RAM in the machine.

So adding 4 GB more RAM will not increase the free RAM. It will just increase the amount of RAM used for caching of file data. Your 600 MB of free RAM is just the result of the actual memory consumption jumping a bit up/down as different processes runs. And when memory is released it ends up as free - until some other program needs it or until the OS will repurpose it as cache.

 

If a program needs more than your 600 MB of memory, then the OS will instantly throw away some cached data and hand over to the program. So you aren't lacking RAM in the system.

[andyjayh]

Ok, thanks for explaining that. I thought it was along those lines but just couldn't find any explanation to confirm.

[John_M]

https://www.linuxatemyram.com/

[andyjayh]

Excellent, thanks for that article, explains it well

[tr3bjockey]

In case anyone wanted to know.  I was worried about unraid using up all the ram for caching.  It kept the cache for over 10 hours until I stopped the array and restarted it.  Once I did that, I captured the graph showing that unraid removed most of the cache in about 8 seconds.

did this on unraid version 6.8.0-rc7

[Tobi4775]

Should i be concerned?
I wont drop lower than 5 GB ram - pretty much idle.