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A deep dive into Debian 13 /tmp: What's new, and what to do if you don't like it

(lowendbox.com)
150 points shaunpud | 2 comments | 29 Aug 25 02:39 UTC | HN request time: 0s | source
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nrdvana ◴[29 Aug 25 04:29 UTC] No.45060203[source]▶
The third mitigating feature the article forgot to mention is that tmpfs can get paged out to the swap partition. If you drop a large file there and forget it, it will all end up in the swap partition if applications are demanding more memory.
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m463 ◴[29 Aug 25 06:10 UTC] No.45060756[source]▶
what swap partition?

I meant this sort of jokingly. I think have a few linux systems that were never configured with swap partitions or swapfiles.

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edoceo ◴[29 Aug 25 06:17 UTC] No.45060793[source]▶
I'm with you. I don't swap. Processes die. OOM. Linux can recover and not lose data. Just unavailable for a moment.
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marginalia_nu ◴[29 Aug 25 07:21 UTC] No.45061182[source]▶
The Linux OOM killer is kinda sketchy to rely on. It likes to freeze up your system for long periods of time as it works out how to resolve the issue. Then it starts killing random PIDs to try to reclaim RAM like a system wide russian roulette.

It's especially janky when you don't have swap. I've found adding a small swap file of ~500 MB makes it work so much better, even for systems with half a terabyte of RAM this helps reduce the freezing issues.

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1. wahern ◴[29 Aug 25 07:33 UTC] No.45061255{4}[source]▶
Yeah. I always disable overcommit (notwithstanding that Linux cannot provide perfectly accurate strict memory accounting), and I'd prefer not to use swap, but Linux VM maintainers have consistently stated that they've designed and tuned the VM subsystem with swap in mind. Is swap necessary in the abstract? No. Is swap necessary on Linux? No. But don't be surprised if Linux doesn't do what you'd expect in the absence of swap, and don't expect Linux to put much if any effort into improving performance in the absence of swap.

I've never ran into trouble on my personal servers, but I've worked at places that have, especially when running applications that tax the VM subsystem, e.g. the JVM and big Java apps. If one wonders why swap would be useful even if applications never allocate, even in the aggregate, more anonymous memory than system RAM, one of the reasons is the interaction with the buffer cache and eviction under pressure.

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2. throw0101c ◴[29 Aug 25 12:01 UTC] No.45062908[source]▶
> […] but Linux VM maintainers have consistently stated that they've designed and tuned the VM subsystem with swap in mind.

There is a citation for this that can be shown to skeptics?