The system has swap disabled.

Linux doesn't really have any distinction between the desktop and underlying OS components in userspace and anything else in userspace. Linux is quite userland-agnostic, and distros have traditionally mixed user software with distro-managed software. You shouldn't use `sudo` to install software by default, your package manager should allow installing software for just your user. Software installed for the system could then be the only software allowed to mark itself as required for interactivity. You could do that manually to other software if you had root access, but "normal" user software installs with the package manager couldn't do so since they wouldn't get root access.

That'd require some new capabilities added, and some substantial shifts in how distro maintainers & users operate, so it's extremely unlikely. It's much closer to how things like Android operate, though still not quite as secure as giving each application its own user & dedicated storage for data.

Alt+[SysRq,f]

Or Alt+[SysRq,h] for help

There is no actual swapping in the modern kernels. Nowadays, it is paging, when the kernel pages out individual unused memory pages, not entire processes, so it keeps all non-blocked processes running, but only necessary memory pages in the memory.

> This is not true.

Yeah that wasn't correct. It will however cause the kernel to refuse memory allocations[1] which could have been allowed, and a lot of programs don't handle that gracefully.

[1]: https://www.kernel.org/doc/html/v6.13/mm/overcommit-accounti...

You're mashing together two groups. One claims having swap is good actually. The other claims you need N times ram for swap. They're not the same group.

> Memory is limited either way; whether it’s RAM or RAM + swap

For two reasons: usage spikes and actually having more usable memory. There's lots of unused pages on a typical system. You get free ram for the price of cheap storage, so why wouldn't you?

This rule of thumb is outdated by two decades.

The proper rule of thumb is to make the swap large enough to keep all inactive anonymous pages after the workload has stabilized, but not too large to cause swap thrashing and a delayed OOM kill if a fast memory leak happens.

> There’s a common rule of thumb that says you should have swap space equal to some multiple of your RAM.

That rule came about when RAM was measured in a couple of MB rather than GB, and hasn't made sense for a long time in most circumstances (if you are paging our a few GB of stuff on spinning drives your system is likely to be stalling so hard due to disk thrashing that you hit the power switch, and on SSDs you are not-so-slowly killing them due to the excess writing).

That doesn't mean it isn't still a good idea to have a little allocated just-in-case. And as RAM prices soar while IO throughput & latency are low, we may see larger Swap/RAM ratios being useful again as RAM sizes are constrained by working-sets aren't getting any smaller.

In a theoretical ideal computer, which the actual designs we have are leaky-abstraction laden implementations of, things are the other way around: all the online storage is your active memory and RAM is just the first level of cache. That ideal hasn't historically ended up being what we have because the disparities in speed & latency between other online storage and RAM have been so high (several orders of magnitude), fast RAM has been volatile, and hardware & software designs or not stable & correct enough such that regular complete state resets are necessary.

> Why? At that point, I already have the same total memory as those with 8 GB of RAM and 8 GB of swap combined.

Because your need for fast immediate storage has increased, so 8-quick-8-slow is no longer sufficient. You are right in that this doesn't mean you need 16-quick-16-slow is sensible, and 128-quick-128-slow would be ridiculous. But no swap at all doesn't make sense either: on your machine imbued with silly amounts of RAM are you really going to miss a few GB of space allocated just-in-case? When it could be the difference between slower operation for a short while and some thing(s) getting OOM-killed?

There is too much focus in this discussion about low memory situations. You want to avoid those as much as possible. Set reasonable ulimit for your applications.

The reason you want swap is because everything in the Linux (and all of UNIX really) is written with virtual memory in mind. Everything from applications to schedulers will have that use case in mind. That's the short answer.

Memory is expensive and storage is cheap. Even if you have 16 GB RAM in your box, and perhaps especially then, you will have some unused pages. Paging out those and utilizing more memory to buffer I/O will give you higher performance under most normal circumstances. So having a little bit of swap should help performance.

For laptops hibernation can be useful too.

Another factor other commenters haven't mentioned, although the article does bring it up: you may disable swap and you will still get paging behavior regardless, because in a pinch the kernel will reclaim pages that are mmapped to files. Most typically binaries and librairies. Which means the process in question will incur a map page read next time it schedules. But of course you're out of memory, so the kernel will need to page out another process's code page to make room, and when that process next schedules... Etc.

This has far worse degradation behavior than normal swapping of regular data pages. That at least gives you the breathing space to still schedule processes when under memory pressure, such as whichever OOM killer you favor.

The reason you're supposed to have swap equal in size to your RAM is so that you can hibernate, not to make things faster. You can easily get away with far less than that because swap is rarely needed.

You're implying that people are telling you to set up swap without any reason, when in fact there are good reasons - namely dealing with memory pressure. Maybe you could fit so much RAM into your computer that you never hit pressure - but why would you do that vs allocating a few GB of disk space for swap?

Also, as has been pointed out by another commenter, 8GB of swap for a system with 8GB of physical memory is overkill.

IMO OOM killing should be reserved for single processes misbehaving. When a lot of different applications just use a decent amount of memory and exhaust the system RAM swapping to disk is the appropriate thing to do.

swap causes thrashing if you have too large swap and no cgroup limits.

There are different definitions of "just work".

That's not so much a rule of thumb as an assessment you can only make after thorough experimentation or careful analysis.