Build time for linux/arm64 image

[tsibley]

The current build time for the linux/arm64 image in CI is around 45 minutes (judging by recent runs). That's pretty long! This is in large part because it's running on amd64 hardware emulating arm64 with QEMU instead of running natively on arm64 hardware.

It's come to my attention (again, but I didn't look into it last time) that we could be running this build on actual arm64 hardware by using GitHub's "large" runners. This would cost us money, as large runners are not included gratis like the standard runners we use now.

We may not want to do this, and that's fine, but I wanted to record it somewhere.

[victorlin]

Maybe we could use macos-14/macos-15 which are ARM-based? If I remember correctly and things haven't changed in a year, running the linux/arm64 build on an M1, even though it still needs some macOS/Linux emulation by Docker, is faster than running the linux/amd64 build.

EDIT: I briefly tried doing something similar in victorlin/github-actions-docker-build#2 but didn't get very far.

[victorlin]

The current CI workflow takes advantage of the multi-platform build happening on a single runner:

docker-base/.github/workflows/ci.yml

Line 55 in 0acdc79

- run: ./devel/build -p linux/amd64,linux/arm64 -r ghcr.io -t "$TAG" -l logs/

Using multiple runners will require separate build commands and additional steps to combine manifests and create the multi-arch image tag. But the added complexity may be worth it!

[tsibley]

Oh, interesting idea to use the arm64 macOS runners. That sounds promising (though maybe comes with enough caveats/sharp edges that using arm64 Linux runners would be worth it?).

But the added complexity may be worth it!

Yeah, that was my thinking too.

[tsibley]

Linux arm64 runners are now available without paying for the larger sizes.