this post was submitted on 19 Feb 2024
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Zram is swap in ram. It uses fast compression to quickly compress memory instead of moving it to disk.
The disagreement here might be a semantic one. When people say "swap" they're usually referring to the swap partition on disk, not just any memory that can be used to "spill" to.
What you are describing with zram serves a fundamentally different function from swap space. If the OS dumps its memory to swap, the PC can lose power and still recover. If it compresses LRU memory to zram, and loses power, it cannot recover.
Both are useful in low memory situations, but swap covers more than that. Most familiar with swap space would agree that its location on a nonvolatile disk rather than in volatile memory is critical to what makes it "swap" space.
"Some of the use cases include /tmp storage, use as swap disks, various caches under /var and maybe many more. :)"
https://docs.kernel.org/6.1/admin-guide/blockdev/zram.html
I think maybe you think I said "zram offers a subset of features of swap space". Rather, zram offers a fundamentally different function from swap space as it resides in memory rather than on disk. It does not and cannot replace the function of disk-based swap space.
Edit: again, I don't want to argue semantics, generally when people say "swap space" they mean the on-disk partition and not just any memory that can be spilled to.
TIL that zram actually does advertise itself as somewhere you can swap to, and generally their terminology is correct, but I think most Linux users colloquially understand swap space as residing in nonvolatile memory.