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There are good use cases for swap. I work with very performance sensitive memory hogging applications that tend to process in bursts as incoming batched data arrives. We also have a lot of required background "security" applications.

Having the idle applications move out to swap so that a significant amount of free RAM to allow for the active, real-time applications to expand into is a major boon. RAM is expensive now, so it's become even more critical to not waste it.

But even in self-hosting at home I take advantage of it since I have a limited number of servers with limited RAM and a bunch of applications and/or docker containers running, many of which don't need to be active at all times, but if they were all active, would have trouble with the limited RAM. Swap allows for inactive applications to free up RAM for the active ones and leave enough available at all times to allow an application to quickly spin up new jobs.

Anyway, sure, for a simple desktop computer without a bunch of junk background applications running for "security" or whatever, and an overabundance of RAM installed, it's probably not useful. But for high performance, memory hungry applications with lots of background stuff running, it can be a big help.

That said, there are use cases where the opposite is useful and using a RAM drive is better than writing to disk for cache and temporary logs when you have enough RAM. My opnsense router for instance uses a RAM drive to store cache and logs (logs are mirrored to the NAS for long term storage, so just the local copy is lost on reboot). That system has enough RAM and I'd rather reduce disk wear, and I don't plan to add too many other applications to that server that it would run low.

I used to be this guy. We have huge amount of memory in our storage server. Why would we need swap? Well, once the system started killing programs I read up on swap and how the system handles its caches, especially ZFS ARC.

Short version is that while the system can evict its caches syncronously, it can only async notify ZFS that it should also shrink its caches, but the out-of-memory killer will start killing before ZFS and its kernel counterpart can start to free up memory.

A tiny bit of swap completely solved this, since swapping is sync for the kernel and the OOM killer will wait for it.

No

It turns out the computer mostly freezes once you go past 200% RAM used.

Yes, swap partitions are shit.

The real hotness is swap drives.

Just the use that your old 64GB SSDs were waiting for!

(Fun fact: in Linux, if you have multiple swap partitions mounted, the kernel will automatically use striping (like RAID) in order to read and write from them as fast as possible. If you have multiple small SSDs used for swap, the read/write speed from swap can actually become pretty fast.)

People still use swap partitions instead of swap files?

All I know is that I had 16GB RAM and 4GB swap and I used to get crashes sometimes.

Set that fucker to 32GB out of spite, now no crashes. No idea why that helped. But I guess I do have like 15 tabs open on the regular (web dev)

"Unresizeable block device at end of disk"

Classically the swap partition was located at the physical middle of the drive so that on average, no matter where the heads where, the swap partition wasn't far away

"I'm not a friggin bear, I don't hibernate!"

swapfile gang

.rw------- root root 4.0 GB Mon Jun  1 04:10:37 2026  /var/swap

Everyone defending swap like crazy in the comments... so let me give a counter argument specifically for desktop:

Many years ago I stopped using swap on all my computers (I exclusively use linux) and the reason is: every time anything regarding interactivity went to swap, my system would freeze and literally become unusable for a really long time until I killed something. Since I got tired if that behaviour I decided I prefer for random shit to die but my computer still be usable.

It wasn't very often, but I don't get OOM killer often either (as in I don't remember the last time it happened and I use linux every day for both work and fun), and the freezing situation was way more annoying, to the point I sometimes ended up cold switching off the computer. I'm surprised on how many people run out of memory constantly. I guess you all are just using linux for servers and have crazy processing of infinite data...

Building a PC in 2026 be like "I cant afford RAM, but I can use a whole TB hard disk I shucked from an old WD external as swap and maybe my PC will feel modern"

SWAP RAM is useful for hibernation mode and fall back ram incase you have low memory.

Once tortured myself with having to go through...

The Android build system. Booo, scary.

I only wanted a LineageOS boot image built. The recommended specs list 64GiB RAM. Figured wouldn't apply to me until I tried to build a target literally called "nothing". It just used up all of the RAM and OOMed about 2 minutes in, building the "build cache" or whatever the fuck it needs to do to "warm up".

After a few fucktons of swapspace, turning off some of my daemons, some sysctl fuckery (there were options for limiting process virtual memory size IIRC? I put it all the way up) and taskset -p 0-15:1 (use logical CPUs 0, 2, 4...), I had my laptop allocating 50 something GiB. I have 16GB (decimal) physical RAM installed and I consider that already way too much for my usual needs.

After about half an hour of the build system build systeming, it just stopped doing that then built the kernel in 4 minutes with everything else in some time too.

Yes, I have tried just running make directly. That just resulted in an image that did nothing but toggle on and off an empty (no percentage) charging circle via power button.

I init a ramdisk and put a swap file there and call it L4 cache

Swap and zram saved my R and Python Dana analysis script a couple of times.

"Hello I would like to torture my SSD's FTL because I left three Electron apps open"

If you don't actually need the swap, Linux isn't going to make use of swap. If you need the swap, then you'd probably rather use it than have the OOM killer take out a process.

My desktop has plenty of swap available, but is using none of it, because the system isn't under memory pressure.

I basically never used swap until I used some script that was supposed to de-duplicate text messages from SMS backups.

Turns out feeding it a 100,000 message archive spanning back 15 years will somehow eat up ~80GB of RAM. I doubt it should, I guess it probably just wasn't optimized for such a large amount.

So I made a 64GB swap file and it completed fine.

Definitely configure swap, but I don't think there is much benefit of a swap partition over a swap file these days and swap files are trivial to configure.

Can anyone tell me why I see swap usage with 10+GB of free RAM available?

My built-in Devil's Advocate has to ask if that's really true? Have you got a citation newer than 2 decades old? Frankly, i find it difficult to believe that anyone wouldn't like to use electron software, for the simple reason that making your SSD suffer is fun.

Edit: in 30 years of administering Linux and (previously) Solaris sytems i've never once had to change HDDs or SSDs, so claims of torture are, i opine, exaggerated. i'll also claim that keeping electron software out of the filesystem is not good for your hygiene.

Then what is the setup if my computer only has 4GB of memory for daily driving? Just curious because swap partitions are what I normally do on limited resource machines.

ACPI S4 Hibernation would like to have a word with you

I don't really need swap until I need to compile blender... Need somewhere around 64Gb (with compression) to deal with the peaks