Reminder: Enable ZRAM on your Linux system to optimize RAM usage

Posted by type0 1 day ago

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Comments

Comment by Kim_Bruning 1 day ago

There's also kernel zswap, right?

https://www.kernel.org/doc/html/latest/admin-guide/mm/zswap....

Oh right, definitely. Chrisdown wrote an article comparing the two:

https://chrisdown.name/2026/03/24/zswap-vs-zram-when-to-use-...

Zswap is supposed to degrade more gracefully.

There's even some HN comments on it:

https://news.ycombinator.com/item?id=47500746

Comment by yjftsjthsd-h 1 day ago

My impression is that zswap will be the universally preferred option for compressed swap, but right now it doesn't work without disk swap behind it?

Comment by dlcarrier 1 day ago

The architecture of zswap does make more sense, because you might as well combine the low speed and latency of compression with the same from writing to storage.

Comment by ChocolateGod 1 day ago

You only want to use zram if you've got no swap device (e.g. a raspberry pi).

If you do, you'll want zswap instead.

Comment by rcxdude 1 day ago

What's old is new again: I remember various hacks like this being popular in early android ROMs because the first android phones really didn't have enough RAM to support the OS well.

Comment by phh 2 hours ago

Well, you stopped hearing about it, not because it stopped being used, but because its support became mainstream for a very long time. Google strongly recommends using zram on all devices, even on devices with a lot of RAM since like Android 10?

Comment by cromka 1 day ago

Asahi devs initially enabled ZRAM by default and then disabled it, now recommending against it, quoting instabilities and random weirdness.

Comment by esperent 1 day ago

I've heard ZRAM mentioned before and I've just spent 5 minutes reading articles on it... Which is about the maximum I have time for these days when it comes to esoteric linux internals.

What's the downside? Does it use much CPU?

If I have enough RAM already, should I still enable it?

One article says it can be mapped to /tmp to reduce i/o. Is that a good idea?

This article is light on all of these kind of details.

Comment by BenjiWiebe 1 day ago

'Swapping' to ZRAM is far less painful than actual disk-backed swap. Sometimes I start wondering why the computer is a bit sluggish, and find that I've got several GB in ZRAM.

Comment by iberator 1 day ago

I remember that back in around 2007 i was able to somehow mount a graphical card (ati similar to geforce2?) memory directly in Linux, and put my swap file there :); Great times. Slackware 8.1 i think.

as for zram: somehow i dislike it. Nowdays ram is plenty and if not: better to have fast OOM than chug of death with swap.

I also remember running NetBSD 1.3.1 and Slackware 3 on 386SZ 26MHZ with 2 mb of ram (nowadays hard limit is 4mb to boot due the large memory pages on x86 afik)

Comment by Neywiny 1 day ago

Much agreed. Early OOM is so much better for me than swap. I have 128G on my work laptop, 96 on my personal desktop. If it doesn't fit in that, it probably means I'd need a terabyte or infinite amount of swap and that's just nonsense.

Comment by sidewndr46 1 day ago

This reminds me of a question I answered on StackOverflow a long time ago. I pointed out the original question was asking the computer to allocate no less than 128 gigabytes of RAM. The poster refused to accept the answer because I "didn't solve the problem, only explained why the code did not work"

Comment by Neywiny 1 day ago

I mean I would indeed consider that a comment on the question rather than an answer. Unless the question was "why doesn't the work with less than 128GB of RAM?"