[chore] Use sccache in builds

[mdboom]

This is an alternative to #1154. Experimenting here and we should pick only one.

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[mdboom]

/ok to test

[leofang]

Looking at the post action cleanup log, we don't seem to be building the cache at all. I suspect on Linux it has to do with cibuildwheel launching a manylinux container, and if so we need to mount sccache into the container. But this does not explain the Windows situation, which does not use container and instead we build wheels on the bare VM.

[leofang]

Do we need to convince setuptools to prepend sccache to CC and CXX?

[mdboom]

Do we need to convince setuptools to prepend sccache to CC and CXX?

Yeah, it looks like this action (unlike the ccache-based one) doesn't install the symlinks. The docs have examples setting CC and CXX. I'll try that and see if setuptools picks it up (I think it normally does).

[mdboom]

/ok to test

[mdboom]

/ok to test

[mdboom]

/ok to test

[mdboom]

/ok to test

[mdboom]

/ok to test

[mdboom]

/ok to test

[mdboom]

/ok to test

[mdboom]

/ok to test

[cpcloud]

Only question is about a possibly-unused variable, but that's not blocking.

[leofang]

/ok to test 7cac30d

[leofang]

/ok to test 6be8df7

[leofang]

It seems neither renaming (6be8df7) nor wrapping (8f6f008) works on Windows...

[leofang]

/ok to test 1eb6a1b

[leofang]

I am thinking we should purge all unsuccessful Windows attempts and get this merged.

[mdboom]

I am thinking we should purge all unsuccessful Windows attempts and get this merged.

I agree.

[mdboom]

/ok to test

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/ok to test

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[mdboom]

/ok to test 6cfe70d

[mdboom]

This is working with the Windows stuff removed.

However, I'm not sure how to confirm it's actually working. The stats at the end of the log (I guess) are from the host so are basically irrelevant.

But I'm also not seeing any speed improvement. For example:

• This run from this PR, presumably with a hot cache, took 227s to build cuda_bindings
• This run from another PR, took 211s to build cuda_bindings

I think the difference is within the noise, but we aren't seeing a notable speedup? If it is really caching, maybe the remote caching overhead of large files is erasing any benefits?

[leofang]

I saw Linux builds decreased from ~9 mins to 5 mins as of commit c10dc60 (link). Let me check what happened since then.

The cache stats need to be accessed in every cibuildwheel's test step (example), not at the end of the build workflows. As already noted, the stats on host is irrelevant.

[leofang]

@mdboom Something caused cache miss in the most recent CI run:

  Compile requests                      41
  Compile requests executed             21
  Cache hits                             2
  Cache hits (C/C++)                     2
  Cache misses                          19
  Cache misses (C/C++)                  19
  Cache hits rate                     9.52 %
  Cache hits rate (C/C++)             9.52 %
  Cache timeouts                         0
  Cache read errors                      0
  Forced recaches                        0
  Cache write errors                     0
  Cache errors                           0
  Compilations                          19
  Compilation failures                   0
  Non-cacheable compilations             0
  Non-cacheable calls                    0
  Non-compilation calls                 20
  Unsupported compiler calls             0
  Average cache write                0.360 s
  Average compiler                  20.770 s
  Average cache read hit             0.173 s
  Failed distributed compilations        0
  Cache location                  ghac, name: c53e4962b46713a17b429097c76c3a9dfe6c94ba4556b3b544ce89beb6872fc9, prefix: /sccache/
  Version (client)                0.12.0

https://github.com/NVIDIA/cuda-python/actions/runs/18753688569/job/53499960916?pr=1156#step:17:1336

I dunno what happened but I see many new caches generated in the last hour or so:
https://github.com/NVIDIA/cuda-python/actions/caches?query=sort%3Acreated-desc

Let me kick off another run to ensure we get cache hits.

[leofang]

/ok to test 6cfe70d

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[mdboom]

Let me kick off another run to ensure we get cache hits.

Cool. Maybe the cache is somehow keyed off the contents of the build-wheel.yml file. It wouldn't be a crazy thing to do.

[leofang]

It wouldn't be a crazy thing to do.

Sounds crazy to me lol... I thought it's only relevant to compiler versions, flags, args, and .cpp file contents, if the cache can be invalidated easily due to workflow changes, it is a bit annoying. GitHub Cache space is only 10 GB and we've been managing it carefully so far. It's a scarce resource.

Anyway, cache hits are back: https://github.com/NVIDIA/cuda-python/actions/runs/18755592039/job/53506633614?pr=1156#step:17:1334

[mdboom]

Anyway, cache hits are back: https://github.com/NVIDIA/cuda-python/actions/runs/18755592039/job/53506633614?pr=1156#step:17:1334

Great. And it looks like a cuda_bindings build is now 55s vs. 220s (approx). So, around 3 minutes saved (+ the time saved on the 2 cuda_core builds). Not bad.

[cpcloud]

I tinkered with sccache locally, and the remaining 55s is mostly spent in the linker, which is a whole other can of worms :)

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