| 21 Oct 2025 |
 Julian | As I am thinking about ways to work around this, I feel like all workarounds are very hacky. Is this wrong caching behaviour that I observed covered by the above mentioned PR? Or would it be an on-going issue without clear solution, because submodules are involved? Just wondering whether there's a feasible fix in the meantime or whether it's a bigger scale on-going issue. | 14:37:45 |
 Sergei Zimmerman (xokdvium) | In reply to @juliankuners:matrix.org
As I am thinking about ways to work around this, I feel like all workarounds are very hacky. Is this wrong caching behaviour that I observed covered by the above mentioned PR? Or would it be an on-going issue without clear solution, because submodules are involved? Just wondering whether there's a feasible fix in the meantime or whether it's a bigger scale on-going issue. Reasonably we could just avoid caching the fetchToStore entry if submodules are present in the local checkout. A more clever solution would be to filter out the empty subdirs for submodules when fetching to the store from a local checkout. The first solution seems more immediate and backportable. Submodules + caching is definitely an ongoing issue | 14:45:20 |
| Julian | Re-looking at the CI logs, it's probably not immediately the checkout problem, as it the mis-cached repository is another repository and not the ceckout (that is also not a submodule or anything) :/. Sorry for the confusion. | 14:48:26 |
| Julian | For clarification. The repositories have submodules, but none are used for nix flakes and derivations. | 14:49:13 |
| Sergei Zimmerman (xokdvium) | I think I understand what’s going on. Will poke around soonish and see | 15:13:25 |
| Julian | Yea, me somwhat too. It is actually the checkout issue, but it's caused by a checkout of the mis-cached repository in another CI on the same CI machine, see here. The timestamp of the CI job and the cache entry in the sqlite database match exactly, same as the wrong nix store path 72alw9m62226brv4v4m98fqrk31mlp34. | 15:21:07 |
| Julian | I created a respective issue, highlighting the I suppose actual root cause, all things considered https://github.com/NixOS/nix/issues/14317 | 17:03:51 |
 dramforever | In reply to @juliankuners:matrix.org
I created a respective issue, highlighting the I suppose actual root cause, all things considered https://github.com/NixOS/nix/issues/14317 oh yeah that's a duplicate of https://github.com/NixOS/nix/issues/13698 | 17:13:40 |
| dramforever | guess i was a few hours late to the discussion | 17:15:47 |
| Julian | Thank you, I missed this one during my issue search. I closed it and linked to it in the respective other issue. | 17:19:57 |
|  @echobc:matrix.org joined the room. | 18:09:44 |
|  mjolnir banned @echobc:matrix.org (<no reason supplied>). | 18:09:44 |
 niksnut | learned today that using std::string for large buffers is very inefficient (huge kernel overhead): https://github.com/DeterminateSystems/nix-src/pull/238/commits/edf45d6e1158a059e7ded5460d2a3947dc35fdf8 | 20:44:48 |
| Sergei Zimmerman (xokdvium) | This is sort of more about doing unnecessary construction/destruction of an object. Not special to std::string in any way | 20:55:40 |
| niksnut | it's a result of having a large contiguous allocation (so it would also affect std::vector<char>) | 20:56:21 |
| Sergei Zimmerman (xokdvium) | Yeah, it's much better to allocate once and reuse that allocation as you did there | 20:56:45 |
