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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 | 3 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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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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k_bx ◴[29 Aug 25 05:47 UTC] No.45060656[source]▶
Disabling swap on servers is de-facto standard for serious deployments.

The swap story needs a serious upgrade. I think /tmp in memory is a great idea, but I also think that particular /tmp needs a swap support (ideally with compression, ZSWAP), but not the main system.

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1. ravetcofx ◴[29 Aug 25 05:54 UTC] No.45060682[source]▶
Swap always seemed more meant for desktop use. Servers you need to give the real memory expected of the application stack.
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2. someothherguyy ◴[29 Aug 25 06:20 UTC] No.45060812[source]▶
plenty of footguns in that general advice, local in memory storage services with default config, etc
3. finaard ◴[29 Aug 25 06:29 UTC] No.45060866[source]▶
Pretty much all the guidelines about swap partitions out there reference old allocator behaviour from way over a decade ago - where you'd indeed typically run into weird issues without having a swap partition, even if you had enough RAM.

Short (and inaccurate) summary was that it'd try to use some swap even if it didn't need it yet, which made sense in the world of enough memory being too expensive, and got fixed at the cost of making the allocator way more complicated when we started having enough memory in most cases.

Nowadays typically you don't need swap unless you work on a product with some constraints, in which case you'd hand tune low memory performance anyway. Just don't buy anything with less than 32GB, and you should be good.