NetBSD ram usage

cam-k

Hi there,

I'm wondering why NetBSD uses so much ram? I have a NetBSD box and it ran for a couple weeks without a reboot, and it seemed to have creeped up to nearly 8GB of ram, with only 10 MB free. It only has one daemon running outside of the base system, dnetc , so it's possible that that is causing the memory leaks, but I've ran other boxes without it and I've always noticed a disproportional amount of ram usage on netbsd compared to the other bsd's, and it always seems to creep up over time.

I also get differing ram usage amounts depending on which program I use to check it. Neofetch, htop and free all give differing amounts and is never the same.

rvp

cam-k Could actually be a memory leak in the kernel (a lot of these were fixed in NetBSD-10). Or, it could be just normal file-caching. The system hasn't been sitting entirely idle for the past 2 weeks. Every day, cron runs the daily script which scans the disk. Then on weekends, the weekly script is run. These usually involve a lot of file I/O.

Can you post the output of this command (as root), so we can see how your RAM is being used?

top -n -o res

NetBSD, by default, uses up to 80% of mem for cacheing. I don't like this and I routinely reduce all caches. In /etc/sysctl.conf, I have:

vm.anonmin=5
vm.anonmax=20
vm.execmax=10
vm.filemin=5
vm.filemax=10
vm.bufcache=5

Then come back in 2 weeks and tell us the results.

push

vmstat should be native memory monitor.

http://netbsd.org/docs/guide/en/chap-tuning.html#tuning-mtools-vmstat

cam-k

push

Yes the free utility in the repo is just a front end for vmstat. they show the same amount of ram usage. So I suppose that is the correct amount? It seems overly inflated, unless NetBSD just allocates memory and does not it free it for whatever reason.

I just turned on my box today and it has nearly used all 8GB of ram, with just 6Megabytes free, with nothing but the base system running. That sounds like a ludicrous amount for a minimal BSD system

push

cam-k
Free is nice and simple, but vmstat is the one.

naguam

The question is, did you feel the system being very slow. Do you have evidence showing it is getting slow as the memory get filled up.

Because it could be just caching for responsiveness. Unused RAM at time T is lost ram.

Also can you try to reproduce the issue without dnetc ?

cam-k

naguam

No I didn't see any evidence of the system getting slow, but it's very concerning to use 7992 MB of ram just to run a basic system. I've never seen any other OS work this way. This is without dnetc and it's been a common denominator among all the NetBSD systems I've used.

But if that is normal behavior then I guess it is fine.

cam-k

push

Free on netbsd is just a shell script that parses vmstat output and uses awk to have it display exactly as you would on a linux system with free.

nettester

Exactly, the most interesting thing about the whole situation is where the RAM ended up being used.

cam-k

![
As it is, free reports 2.8GB of ram usage.

I've made those changes in /etc/sysctl.conf too, and I'll come back in 2 weeks and see what happens.

rvp

cam-k 1161 MB of file-cache is normal after /etc/daily runs. On a QEMU 4GB VM with the settings I gave before, I see this:

$ top -n -o res | head -n6
load averages:  0.00,  0.00,  0.00;               up 0+00:04:22        08:04:24
5 processes: 4 sleeping, 1 on CPU
CPU states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
Memory: 92M Act, 4K Wired, 14M Exec, 51M File, 3768M Free
Swap: 8000M Total, 8000M Free / Pools: 47M Used / Network: 

$ sudo sh -c 'umask 022; sh /etc/daily >/dev/null 2>&1'

$  top -n -o res | head -n6
load averages:  0.41,  0.11,  0.04;               up 0+00:05:11        08:05:13
5 processes: 4 sleeping, 1 on CPU
CPU states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
Memory: 1637M Act, 216K Inact, 4K Wired, 15M Exec, 1590M File, 1609M Free
Swap: 8000M Total, 8000M Free / Pools: 659M Used / Network: 

$

That's 51 MB of file-cache before /etc/daily runs and 1590 MB afterwards. I have more files on the disk, so more data goes into the file-cache.

nia

As it is, free reports 2.8GB of ram usage.

You can see from your screenshot that around half of this is being used to cache files (File line in top)