Trying to understand LXC RAM and SWAP allocation

[Sandbo]

I have a workstation with 256 GB RAM, and by default the host has only 8 GB SWAP.
With the two LXCs I have, as they can potentially use a lot of RAM, I committed 192 GB RAM and 64 GB SWAP to both.

My question is, in a situation where both LXC reaches a high usage and they consume more than 256 GB in total, are they able to use their individual space for accessing the 64 GB SWAP?
I read somewhere that the way it works is, the LXC's SWAP can only sum up to the host (which is 8 GB here). To make it really works, should I increase the host SWAP size first?

 

[leesteken]

As I understand it: at the moment the maximum swap of a LXC is equal to the memory setting plus the swap setting. In your case: 192GB + 64GB = 256GB of swap allowed by each container and it also has a maximum of 192GB of actual memory.
And yes, all containers together are limited to the size of the actual host swap space. In your case (because of the reason above): the containers require 512GB of host swap space on disk but are limited to the actual 8GB available (that is 8GB together, not necessarily 4GB each), minus any swap used by the host ofcourse.

 

[Sandbo]

As I understand it: at the moment the maximum swap of a LXC is equal to the memory setting plus the swap setting. In your case: 192GB + 64GB = 256GB of swap allowed by each container and it also has a maximum of 192GB of actual memory.
And yes, all containers together are limited to the size of the actual host swap space. In your case (because of the reason above): the containers require 512GB of host swap space on disk but are limited to the actual 8GB available (that is 8GB together, not necessarily 4GB each), minus any swap used by the host ofcourse.

Thanks a lot, I think I am clear about how it allocates now.
In this case, I will probably get a dedicated SSD for doing the SWAP in case we hit a high usage scenario.