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nixpkgs/ci/eval
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Wolfgang Walther 8a39ce4a48
workflows/eval: diff outpaths immediately 
This moves the diff of outpaths into the outpaths job, mainly as a
preparation to allow future improvements. For example, this will allow
running the purity release checks only on changed outpaths instead of
the whole eval.

This also removes the inefficiency introduced in the last commit about
uploading the intermediate paths twice. Now, only the diff is passed on.

Also, technically, the diff is now run in parallel across 4 jobs. This
should be *slightly* faster than before, where outpaths from all systems
were combined first and then diffed. It's probably only a few seconds,
though.
2025-05-25 19:26:08 +02:00
..
compare workflows/eval: diff outpaths immediately 2025-05-25 19:26:08 +02:00
default.nix workflows/eval: diff outpaths immediately 2025-05-25 19:26:08 +02:00
diff.nix workflows/eval: diff outpaths immediately 2025-05-25 19:26:08 +02:00
README.md workflows/eval: load supportedSystems from JSON file 2025-05-11 22:22:45 +02:00

README.md

Nixpkgs CI evaluation

The code in this directory is used by the eval.yml GitHub Actions workflow to evaluate the majority of Nixpkgs for all PRs, effectively making sure that when the development branches are processed by Hydra, no evaluation failures are encountered.

Furthermore it also allows local evaluation using

nix-build ci -A eval.full \
  --max-jobs 4 \
  --cores 2 \
  --arg chunkSize 10000 \
  --arg evalSystems '["x86_64-linux" "aarch64-darwin"]'
  • --max-jobs: The maximum number of derivations to run at the same time. Only each supported system gets a separate derivation, so it doesn't make sense to set this higher than that number.
  • --cores: The number of cores to use for each job. Recommended to set this to the amount of cores on your system divided by --max-jobs.
  • chunkSize: The number of attributes that are evaluated simultaneously on a single core. Lowering this decreases memory usage at the cost of increased evaluation time. If this is too high, there won't be enough chunks to process them in parallel, and will also increase evaluation time.
  • evalSystems: The set of systems for which nixpkgs should be evaluated. Defaults to the four official platforms (x86_64-linux, aarch64-linux, x86_64-darwin and aarch64-darwin).

A good default is to set chunkSize to 10000, which leads to about 3.6GB max memory usage per core, so suitable for fully utilising machines with 4 cores and 16GB memory, 8 cores and 32GB memory or 16 cores and 64GB memory.

Note that 16GB memory is the recommended minimum, while with less than 8GB memory evaluation time suffers greatly.