Swap does not start

[offei]

Memory is 90% used, but swap is still not enabled

https://forum.proxmox.com/javascript:;

 

[Chris]

Hi,
please post the output of cat /proc/swaps and check the value in cat /proc/sys/vm/swappiness, which controlls how aggressively the kernel tries to swap. Default should be 60. Also check and share the output of free -m.

 

[offei]

 

[Chris]

View attachment 46577

Did you set up the swap just now? In that case give the kernel time to swap out pages not used. This will not happen right away.

 

[offei]

Yes, I set up swap a few hours ago
But my other server has been running for several days and is still not using swap

 

[offei]

It's been 12 hours and swap is still not enabled. Do I need to restart pve?

 

[Chris]

It's been 12 hours and swap is still not enabled. Do I need to restart pve?

View attachment 46603

Hm, are you running ZFS on those servers?

If so you can limit the memory ZFS is allowed to consume for caches: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#sysadmin_zfs_limit_memory_usage

See also https://forum.proxmox.com/threads/swappiness-value-is-being-ignored-100-ram-being-used.95598/

 

[offei]

My physical memory is not enough, I have to use swap to be able to, now how to open swap is a problem, is it necessary to restart it?

 

[Chris]

My physical memory is not enough, I have to use swap to be able to, now how to open swap is a problem, is it necessary to restart it?

No, a restart will not have an effect in this case. As I stated before, swap might behave unexpectedly in combination with ZFS, see https://forum.proxmox.com/threads/swappiness-value-is-being-ignored-100-ram-being-used.95598/

Here the recommendation would be to reduce the ZFS ARC cache limits in order to gain some more memory for other processes.

In general, swap is not recommended as it will have a huge performance impact, especially for VMs.

 

[offei]

I have 128 gigabytes of RAM. How much should I limit?
echo "$[10 * 1024*1024*1024]" >/sys/module/zfs/parameters/zfs_arc_max

Is 10G okay? Like This?

 

[Chris]

I have 128 gigabytes of RAM. How much should I limit?
echo "$[10 * 1024*1024*1024]" >/sys/module/zfs/parameters/zfs_arc_max

Is 10G okay? Like This?

As stated in the docs, a rule of thumb is about 2GiB min + 1GiB for each 1TiB of storage. So if the ARC is for the 1.3TiB of storage, than 10GiB should be fine.

echo "$[10 * 1024*1024*1024]" >/sys/module/zfs/parameters/zfs_arc_max

Yes, note however that this will not apply if you reboot, but for a first test it is fine. To make it persistent after reboot, you have to set it via option to the zfs kernel module, as described in the docs.

 

[offei]

Thank you very much. Memory usage is down. I also have a server that is not using ZFS and swap is still not enabled

https://forum.proxmox.com/javascript:;

 

[Chris]

Thank you very much. Memory usage is down. I also have a server that is not using ZFS and swap is still not enabled
View attachment 46624
https://forum.proxmox.com/javascript:;

Well, here actually you have about 502 MiB swapped out, so the kernel is using it, just not aggressively. What is your swappiness in this case?

 

[offei]

He has been working for several days

https://forum.proxmox.com/javascript:;