Memory usage statistics

[sheshman]

Hello,

If this asked before sorry i couldn't find related topic.

I'm using proxmox ve and datacenter as well my server is HP DL360-G9 with 256 GB DDR3 Memory, when i look at the memory status on pve dashboard it shows that approx. 130GB in use

only 4 vm is activated and their memorys are 16+32+32+8 = 88GB, also datacenter shows as similiar usage


But on the htop side through ssh it shows like this



Proxmox's itself also using memory for core services etc. but why it shows this huge difference?

 

[Impact]

I don't know at the top of my head what it uses to calculate this but I'd check the Memory Usage and Host Memory Usage columns in Datacenter > Search.

 

[Impact]

Does the node's Summary > RAM usage line up with the value? I just checked and mine does so it seems to just summarize that. Kinda obvious in hindsight.
HTOP doesn't count ZFS' ARC as used. Do you use ZFS? Also check the node > Summary > Memory Usage graph which breaks this down a bit.

 

[sheshman]

Does the node's Summary > RAM usage line up with the value? I just checked and mine does so it seems to just summarize that.
HTOP doesn't count ZFS' ARC for example. Do you use ZFS? Also check the node > Summary > Memory Usage graph.

no it doesn't match and yes using ZFS

 

[Impact]

That looks like it matches to me?


Seems like you use an older PVE version. Modern ones break this down like this


Check the ARC status of zarcsummary -s arc | less or arcsummary -s arc | less to see how much is used by ARC.
You can also add these meters to HTOP via F2

 

[daanw]

ZFS on Linux claims 50% of the system memory for ARC by default.
You can change this to your liking by setting the zfs_arc_max parameter.

For example, to set 64 GB (1024^3*64) as max on a running system:
echo 68719476736 >> /sys/module/zfs/parameters/zfs_arc_max

To make this persistent across reboots, create a file /etc/modprobe.d/zfs.conf and add a line: options zfs zfs_arc_max=68719476736.
Then: update-initramfs -u -k all.

 

[Impact]

The percentage depends on a few things but the new PVE default is 10% and for ZoL it's max(total_memory - 1GB, 5/8 × total_memory). I also have a snippet here to easily alter it. I didn't post it before because I don't see a good reason to alter it.

 

[daanw]

Yes, great that this was addressed. But the old default might still be in place in OP's PVE.
It might be something else, but people wondering about 50 plus a bit % memory usage on a system using ZFS are quite common.