Qemu builds in Github Actions are super slow

[tropic rapids]

Qemu builds in Github Actions are super slow. A build that normally takes 40 seconds running natively is taking 14 minutes under QEMU emulation. Has anyone faced this and was able to fix it?

[fickle wolf]

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[fresh pivot]

That's to be expected. Emulation is not performant at all. If your project is public, then Linux ARM runners should be available for free; otherwise, if the project is private you have no other option than to host your own runner until ARM runners becomes available for private projects as well.

One thing you could play around with is to change the build platform for unrelated stages if you use docker buildx.

For example I do that in my Dockerfile:

FROM --platform=$BUILDPLATFORM node:22-alpine@sha256:5539840ce9d013fa13e3b9814c9353024be7ac75aca5db6d039504a56c04ea59 AS base
# ...
FROM --platform=$BUILDPLATFORM base AS builder
# ...
FROM --platform=$BUILDPLATFORM base AS installer
# ...
FROM node:22-alpine@sha256:5539840ce9d013fa13e3b9814c9353024be7ac75aca5db6d039504a56c04ea59 AS runner