AX86U RAM usage?

[SteverinoLA]

I recently got upgraded from an AX55 to a AX86U. I was plagued with out of memory and many out of space errors in the logs, even after disabling every possible option (QOS, traffic, web history, etc). Reviewing the specs I see that the budget AX55 has only 256G RAM and 128MB ROM. So I decided to upgrade to the AX-86S b/c I don't need 2.5G but then at last minute realized that the U version doubles the RAM from 512 to 1G so went with 86U.

No more out of memory or out of disk space errors to be found, even with every possible option turned on. But I'm curious how the 86U uses it's RAM. A fresh reboot results in an even 512MB used and 512MB free, but then as time goes on, it's all the way up to 987MB used and just 37MB free. What is the 86U doing with all this RAM? Can I assume that, like Windows, it's using the extra RAM for caching and other good things?

 

[ColinTaylor]

Unused memory will be used as disk cache. So if you have a USB storage device connected to the router the memory usage will increase over time as more and more disk blocks are cached, up to ~97%.

Do note however, that when you log into the router's GUI it will usually clear the cache as indicated by a kernel: httpd (xxxx): drop_caches: 1 message in the log. This reduces the memory usage back down to ~44% (depending on how the router is configured).

 

[SteverinoLA]

Ah, I did indeed start to notice this after I plugged in a USB drive. OK, good job Asus!

 

[Tech9]

OK, good job Asus!

If you start pushing this USB drive too much with NAS-like multi GB transfers, your router will still run out of RAM and core services will start crashing. Asuswrt file share is not a NAS, but for occasional light use. Don't keep critical or irreplaceable data on this USB drive.

 

[SteverinoLA]

Ouch, then I withdraw my compliment for Asus, lol. I don't use it as a NAS, just for occasional backups and maybe some media playing.

 

[Tech9]

Ouch, then I withdraw my compliment for Asus, lol.

You've got a router with USB ports + some marketing around it. Use it as router for best results. Get a NAS for your data, if it's important.

 

[bbunge]

I agree with tech9 about getting a NAS. However, if you are concerned about RAM use a swap file or partition on a thumb drive will help.

 

[SteverinoLA]

I'm very concerned about out of space or out of memory errors in the log (like "I got a/AX55) but no concern at all w/RAM usage if it's being put to good use. It does seem odd that USB drive caching is high priority and would push out required processes though.

 

[ColinTaylor]

I'm very concerned about out of space or out of memory errors in the log (like "I got a/AX55) but no concern at all w/RAM usage if it's being put to good use. It does seem odd that USB drive caching is high priority and would push out required processes though.

It's not high priority, in fact it's the opposite. Personally I've never experienced any out of memory conditions on my RT-AX86U, but then I run a very simple setup. So as they say, YMMV.