| 28 Oct 2025 |
 Vladimír Čunát | We're not going easy on rebuids in master. (and the openssl default update has not been merged (yet)) | 08:56:26 |
| Vladimír Čunát | I guess part of that could be avoided by reverting
https://github.com/NixOS/nixpkgs/pull/456027#issuecomment-3455288157 | 08:59:29 |
 emily | vcunat: sorry about the aliases in NixOS tests thing, will take a look | 16:56:29 |
| Vladimír Čunát | context: https://github.com/NixOS/nixpkgs/pull/456065#issuecomment-3457488163 | 16:56:58 |
| emily | lack of CI coverage for NixOS eval is really sad | 16:58:23 |
| Vladimír Čunát | It's expensive. | 16:59:57 |
| Vladimír Čunát | Takes more than one hour on Hydra. Part of that is a huge postgresql transaction, but the eval costs are really high. | 17:00:31 |
| Vladimír Čunát | I think it's OK that some classes of errors don't get caught by CI but only through Hydra/channels. | 17:02:25 |
| emily | yeah, not saying it's easily solvable | 17:03:34 |
| emily | but it would be really nice if it was solved | 17:03:40 |
| emily | has anyone ever looked at if evaluating all the NixOS tests has some specific hot spot? | 17:04:03 |
| emily | is it instantiating a billion Nixpkgs? just the module system being slow? | 17:04:13 |
 K900 | It is both | 17:04:18 |
| K900 | I tried https://github.com/K900/nixpkgs/tree/less-nixpkgses and somehow in our testing on forkos hydra it made things worse | 17:04:38 |
| Vladimír Čunát | Wolfgang Walther is also looking at it, apparently. | 17:04:39 |
| Vladimír Čunát | Let's see who's faster 😅 | 17:04:52 |
| K900 | Which makes no fucking sense | 17:04:57 |
| emily | Hydra eval is parallelized with nix-eval-jobs, right? | 17:05:51 |
| emily | is anything shared between the evaluations of multiple NixOS tests? | 17:05:58 |
| Vladimír Čunát | I'm more worried about the expenses to run all the tests. | 17:06:29 |
| Vladimír Čunát | Because I can see the huge difference between e.g. trunk and trunk-combined. | 17:06:42 |
| Vladimír Čunát | We're spending a surprising amount of Hydra's "real time" on the added tests. | 17:07:04 |
| Vladimír Čunát | Hydra's eval itself tends not to be a real bottleneck. (though in CI it would be bad) | 17:08:03 |
| Vladimír Čunát | * Hydra's eval itself tends not to be a real bottleneck. (though in CI it would be very bad) | 17:08:14 |
 dish [Fox/It/She] | is there no way to parallelize the transaction by splitting it? | 17:35:27 |
| Vladimír Čunát | It would certainly help with the deadlocks and blocking other updates to the DB. | 17:36:33 |
| Vladimír Čunát | It often happens that Hydra stalls for several minutes because of such huge write transaction just happening. | 17:37:14 |
| K900 | There definitely is | 17:39:53 |
| K900 | Hydra is just an ancient Perl monstrosity | 17:40:00 |
 hexa | lol, I remember getting yelled at for nuking old aliases a while ago | 17:40:36 |
