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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 | 1 comments | 29 Aug 25 02:39 UTC | HN request time: 0.209s | 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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buckle8017 ◴[29 Aug 25 04:31 UTC] No.45060224[source]▶
Which is a great reason to have a big swap file now.
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gnyman ◴[29 Aug 25 05:24 UTC] No.45060524[source]▶
Note though that if you don't have swap now, and enable it, you introduce the risk of thrashing [1]

If you have swap already it doesn't matter, but I've encountered enough thrashing that I now disable swap on almost all servers I work with.

It's rare but when it happens the server usually becomes completely unresponsive, so you have to hard reset it. I'd rather that the application trying to use too much memory is killed by the oom manager and I can ssh in and fix that.

[1] https://docs.redhat.com/en/documentation/red_hat_enterprise_...

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1. mnw21cam ◴[29 Aug 25 08:35 UTC] No.45061646[source]▶
That's not true. Without swap, you already have the risk of thrashing. This is because Linux views all segments of code which your processes are running as clean and evictable from the cache, and therefore basically equivalent to swap, even when you have no swap. Under low-memory conditions, Linux will happily evict all clean pages, including the ones that the next process to be scheduled needs to execute from, causing thrashing. You can still get an unresponsive server under low memory conditions due to thrashing with no swap.

Setting swappiness to zero doesn't fix this. Disabling swap doesn't fix this. Disabling overcommit does fix this, but that might have unacceptable disadvantages if some of the processes you are running allocate much more RAM than they use. Installing earlyoom to prevent real low memory conditions does fix this, and is probably the best solution.