> zram, formerly called compcache, is a Linux kernel module for creating a compressed block device in RAM, i.e. a RAM disk with on-the-fly disk compression. The block device created with zram can then be used for swap or as a general-purpose RAM disk
To clarify OP's represention of the tool, it compresses swap space not resident ram. Outside of niche use-cases, compressing swap has overall little utility.
Incorrect, with zram you swap ram to compressed ram.
It has the benefit of absorbing memory leaks (which for whatever reason compress really well) and compressing stale memory pages.
Under actual memory pressure performance will degrade. But in many circumstances where your powerful CPU is not fully utilized you can 2x or even 3x your effective RAM (you can opt for zstd compression). zram also enables you to make the trade-off of picking a more powerful CPU for the express purpose of multiplying your RAM if the workload is compatible with the idea.
PS: On laptops/workstations, zram will not interfere with an SSD swap partition if you need it for hibernation. Though it will almost never be used for anything else if you configure your zram to be 2x your system memory.
> Incorrect, with zram you swap ram to compressed ram.
That reads like what they said? You reserve part of the RAM as a swap device, and memory is swapped from resident RAM to the swap ramdisk, as long as there’s space on there. And AFAIK linux will not move pages between swap devices because it doesn’t understand them beyond priority.
Zswap actually seems strictly better in many cases (especially interactive computers / dev machines) as it can more flexibly grow / shrink, and can move pages between the compressed RAM cache and the disk swap.
To clarify OP's represention of the tool, it compresses swap space not resident ram. Outside of niche use-cases, compressing swap has overall little utility.