Zram Performance Analysis
14 comments
·October 23, 2025burch45
Dylan16807
In the first benchmark it gets a ratio of 4 instead of 2.7, fitting 36-40% more data with 75% more CPU. It looks great.
The next two show it fitting 20% more data with 2-3x the CPU, which is a tougher tradeoff but still useful in a lot of situations.
The rest of the post analyzes the CPU cost in more detail, so yeah it's worse in every subcategory of that. But the increase in compression ratio is quite valuable. The conclusion says it "provides the highest compression ratio while still maintaining acceptable speeds" and that's correct. If you care about compression ratio, strongly consider zstd.
buildbot
I have had similar experience, with ZFS zstd dropped IOPs and throughput by 2-4x compared to lz4! On a 64 core Milan server chip…
1oooqooq
the context is missing.
but for vps, where the cpu usage is extremely low and ram is expensive, it might make sense to sacrifice a little performance for more db cache maybe. can't say without more context
kragen
An alternative is zswap https://old.reddit.com/r/linux/comments/11dkhz7/zswap_vs_zra... which I believe, despite the name, can also compress RAM without hitting disk.
mscdex
It's only an alternative if you have a backing swap device. zram does not have this requirement, so (aside from using no compression) it's basically the only solution for some scenarios (e.g. using entire disk(s) for ZFS).
kragen
Can't you use a ramdisk as your backing swap device?
PhageGenerator
Using a ramdisk for zswap is basically just zram with extra steps.
heavyset_go
If you use hibernation, I think it also compresses your RAM image for potentially less wear and faster loading/saving
1oooqooq
why hibernation would not compress to begin with? you're more likely just end up running zstd twice.
heavyset_go
Swap isn't compressed by default, hibernation dumps memory to swap
sirfz
a comment here about zram caught my eye a day or two ago and I've been meaning to look into it. Glad to see this post (and I'm sure many others saw the same comment and shared my obsession)
mjunyeopkim
[dead]
This post’s conclusions are odd. It has a bunch of extensive benchmarks showing that zstd is by far the worst performing across every metric except a slight increase in compression ratio and then says the conclusion is zstd is the best choice. Unless I’m missing something in the data.