Buildroot:Top Level Parallel Build

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This page documents the effort to support top-level parallel build in Buildroot.

Core support

The core support has been submitted in its v7 iteration at http://patchwork.ozlabs.org/project/buildroot/list/?series=83747. However, this core support does not fix a number of package-specific issues that arise with per-package directory support, and those fixes will be submitted separately.

This patch series is also visible at https://github.com/tpetazzoni/buildroot/tree/ppsh-v7

Per-package directory fixes

All the fixes that we currently have are available at https://github.com/tpetazzoni/buildroot/tree/ppsh-v7-work. This branch is regularly rebased.

  • Issues with Python modules
    • Need to avoid using Python Eggs for host Python setuptools packages. SUBMITTED at http://patchwork.ozlabs.org/project/buildroot/list/?series=83776
    • Need to rewrite _sysconfigdata.py before building a Python module. PENDING until the core support is merged. It is fixed by package/pkg-python: fix for per-package directories
  • Issues with Meson packages
  • Issues with apr/apr-util/apache packages
    • These issues are fixed by a number of fixups. PENDING until the core support is merged. It is fixed by package/apr-util: fix build with per-package directories and package/apache: fix build with per-package directory support in our branch.
  • Issue with the owfs package
    • Needs a _sysconfigdata.py fixup. PENDING until the core support is merged. It is fixed by package/owfs: fixup Python sysconfigdata for per-package directories in our branch.
  • Issue with the cargo package

Known remaining issues

  • The Qt5 packages are broken with per-package directory support. See the thread at http://lists.busybox.net/pipermail/buildroot/2018-December/237727.html for details.
  • The build-time.log file is appended concurrently by multiple packages, probably not good.
  • The package-file-list*.txt files are appended concurrently by multiple packages, probably not good.
  • Some kconfig packages do not have a proper dependency on ccache if ccache support is enabled. This is however not strictly speaking a per-package directory issue.

Testing

To test top-level parallel-build:

  1. Grab the branch at https://github.com/tpetazzoni/buildroot/tree/ppsh-v7-work
  2. Enable BR2_PER_PACKAGE_DIRECTORIES in your Buildroot configuration
  3. Run your build with make -jX

Note that the output will be garbled, as the output of multiple packages building in parallel will be mixed together. You can decide to build with make -jX --output-sync=target to have a cleaner output.

Graphing

To visualize how well (or not so well) your build is parallelized, you can run at the end of a clean build:

  1. make graph-build-time
  2. evince output/graphs/build.timeline.pdf