ZRam instead of ZSwap

[stevefan1999-personal]

I don't need to have swaps on disk yet but I would love to see if we can use zram instead. For a server, compressed memory makes so much sense because a lot of long running tasks generates a lot more redundant data that can be compressed or even memory altogether if their content is identical (deduplication)

[smira]

zswap is more modern/preferred over zram today.

[stevefan1999-personal]

hmm then we will need to take zram into the consideration matrix

[smira]

zswap can be enabled independent of block device swap.

[Noah-Kennedy]

zswap is more modern/preferred over zram today.

I'm just getting into experimenting with Talos, but I'd love to use zram with it.

Having used both a fair bit and worked around their respective tradeoffs, I wouldn't say it's necessarily true that zswap is better or preferred over zram. They are different tools with different sets of tradeoffs, and neither is really superior to the other.

Zswap is really great when you have a lot of solid, enterprise SSD space and uncompressable pages are something you are expecting to be a significant proportion of your space, but neither are always true. For cases where low-end flash is involved like @stevefan1999-personal asked about, I would actually say zram is generally better. This is not dissimilar to my workload, where I have a bunch of Raspberry Pis I am using to play around with Talos before I try it on anything more serious.

Side note: zram can also be used for tmpfs, which is incredibly useful.

Is it possible to use zram right now with Talos, and if so, how?

[smira]

No, zram is not supported as of right now.

I believe zswap handles tmpfs just fine, so not sure what exactly is the difference.

[MrDrMcCoy]

@smira Zswap does indeed handle tmpfs well, but it also requires some sort of regular swap backing device. The purpose of zswap according to the kernel docs is to create a compressed zpool between regular pages and a swap device to partially serve as a writeback cache. You can't writeback to nothing if you want your memory pages to stay safe.

The requirement for a backing swap device for zswap has been the conventional wisdom of experts across multiple distros since the feature was introduced. In my personal experience, if zswap is configured to use up to 50% of a system's 16GB RAM, it will still only let you use 1MB of zpool if your backing swap device is 1MB. Because of this, there is absolutely value in supporting both zswap and zram. For example, if Talos is running on an SBC whose fast storage is dedicated to Ceph and slow boot media either cannot be configured for swap or would be too slow/small for regular swap, zram swap is pretty much the only option.

Please consider adding support for zram swap, as well as providing a facility for configuring the size and compression algorithm. Many of your user's environments, including my own, would greatly stand to benefit from having it as an option. :-)