How limit cpu of docker buildx build？

[darklinght]

When using docker buildx build to create an image, it can cause the computer's CPU to max out. Are there any ways to limit CPU usage during the build process?

[mg1986jp]

A few options depending on your driver:

If you're using the docker-container driver (the default for docker buildx create), the builder itself runs as a container. You can limit its CPU after it's created:

docker update --cpus 4 buildx_buildkit_<builder-name>0

You can also set max-parallelism in a buildkitd.toml to control how many build steps run concurrently:

[worker.oci]
  max-parallelism = 4

Then create the builder with:

docker buildx create --config ./buildkitd.toml

If you're using the default docker driver, the build runs inside the Docker daemon process itself and there's no clean way to cap its CPU from buildx. In that case you'd probably want to switch to docker-container driver so you can control it.

[disdorqin]

Hi — I think the key distinction is that Buildx does not throttle CPU per build by default: the work runs inside BuildKit's daemon (buildkitd), which uses all available cores unless the daemon's container or runtime is resource-constrained.

First check what is actually running:

docker buildx ls
docker buildx inspect
docker info

If you use the docker-container driver, the builder is a container, so you can cap it by limiting the buildkitd container's resources (via the container runtime's CPU quota or BuildKit's resource settings) when you create the builder. The docker driver instead shares the Docker daemon's own limits.

Could you share the output of docker buildx version, the active driver shown by docker buildx ls, and how you currently create the builder? That will let me point to the exact flag or cgroup setting for your setup.

[crazy-max]

Resource limits can now be set for CPU and memory using the --resource flag in build and the resource key in bake commands. This feature requires BuildKit v0.31.0+ and Dockerfile v1.25.0+.

More info: https://docs.docker.com/reference/cli/docker/buildx/build/#resource