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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: 0.001s | source
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ars ◴[29 Aug 25 04:24 UTC] No.45060177[source]▶
File is tmpfs will swap out if your system is under memory pressure.

If that happens, reading the file back is DRAMATICALLY slower than if you had just stored the file on disk in the first place.

This change is not going to speed things up for most users, it will slow things. Instead of caching important files, you waste memory on useless temporary files. Then the system swaps it out, so you can get cache back, and then it's really slow to read back.

This change is a mistake.

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imp0cat ◴[29 Aug 25 04:31 UTC] No.45060221[source]▶
Most systems probably aren't having problems with insufficient RAM nowaday though, do they? And this will reduce wear on your SSD.

Also, you can easily disable it: https://www.debian.org/releases/trixie/release-notes/issues....

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magicalhippo ◴[29 Aug 25 05:09 UTC] No.45060434[source]▶
If you're running it in a VM you might not have all that luxurious RAM.

When my Linux VM starts swapping I have to either wait an hour or more to regain control, or just hard restart the VM.

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1. mhitza ◴[29 Aug 25 06:09 UTC] No.45060754[source]▶
What distro are you running? systemd-oomd kills processes a bit quicker than what came before (a couple minutes of a slow, stuttery system). Still too slow for a server you'd want to have back online as quickly as possible.

At least now when I run out of memory it kills processes that consume the most memory. A few years back it used to kill my desktop session instead!

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2. mnw21cam ◴[29 Aug 25 08:54 UTC] No.45061775[source]▶
Right, that's traditionally been because the X server has typically had a fairly large footprint, and therefore has been very attractive for the oom killer. But in the last 15 years or so, some heuristics have been applied to deliberately discourage the oom killer from killing "important things".

I install earlyoom on systems I admin. It prevents the low-memory thrashing by killing things while the system is still responsive, instead of when the system is in a state that means it'll take hours to recover.