Methods for speeding up build time in a project using bitbake?

Question

I'm working in a project which has many bitbake recipes and takes a lot of time - up to 13 hours in some cases. I am new to bitbake and I'm asking for some way to:

• check what packages take more to build
• check very long dependencies (I have used bitbake -g already)
• check if there are any circular dependencies and how to solve them
• check if there are recipes which aren't used and how to safely remove them

or any suggestions for using any tools for better managing and understanding recipes.

Or any methods/ways for speeding up the build process in general.

Both suggestions and exact techniques are welcomed.

EDIT date 07/08/2013:

Found this useful tool for tracking dependencies

https://github.com/scottellis/oe-deptools

Description:

./oey.py -h

Usage: ./oey.py [options] [package]

Displays OE build dependencies for a given package or recipe.
Uses the pn-depends.dot file for its raw data.
Generate a pn-depends.dot file by running bitbake -g <recipe>.

Options:
-h      Show this help message and exit
-v      Show error messages such as recursive dependencies
-r      Show reverse dependencies, i.e. packages dependent on package
-f      Flat output instead of default tree output
-d <depth>      Maximum depth to follow dependencies, default and max is 10
-s      Show child package dependencies that are already listed
        as direct parent dependencies.

Provide a package name from the generated pn-depends.dot file.
Run the program without a package name to get a list of
available package names.

Answer 1

This is a very broad question!

First, here is a summary on how to inspect your build performance and dependencies when using the openembedded/yocto project. This answers the first part of the question.

What packages take more time to build?

Use the buildstats with the pybootchartgui tool produce a build chart.

Details:

Set USER_CLASSES += "buildstats" in your $BUILDIR/conf/local.conf file. This will dump detailed performance data in $BUILDDIR/tmp/buildstats/<DATE>. Next use the pybootchartgui.py script (in poky/scripts/pybootchartgui) to generate the chart. This will help you localize possible bottlenecks in the build. Of course, if you have a lot of recipes to bake, your chart will be huge. To remove some noise use the -m MINTIME command line option.

For example:

poky/scripts/pybootchartgui/pybootchartgui.py -m 600 $BUILDDIR/tmp/buildstats/201312310904

will only display tasks (do_compile, do_fetch, etc.) that take longer than 10 minutes (600 seconds) to run.

How to check for package dependencies?

To explore the dependencies of a particular package use the depexp utility. For example, to explore the dependencies of eglibc use:

bitbake -g -u depexp eglibc

This will give a better understanding of what each recipe depends on at both run and compile time.

How to check if there are any circular dependencies and how to solve them?

bitbake automatically detects circular dependencies and prints an error message when such a thing happens. The error message contains the name of the packages causing this circular dependency.

How to check if there are recipes which aren't used and how to safely remove them?

bitbake calculates dependencies automatically and won't build packages which aren't needed by your target. If you find some unwanted packages in your image and you wish to remove them:

1. use bitbake -g -u depexp <TARGET> to inspect how the package gets pulled in
2. modify the needed recipes in your layer (by creating a bbappend for example) to eliminate the dependency manually

Improving overall build performance

Finally, some tips on how to improve the overall build performance. This answers the second part of the question.

• Clean up your dependencies (bitbake -g -u depexp <TARGET> is your friend). Building less stuff takes less time.
• bitbake can automatically cache the build outputs and use it for future builds, this cache is called the "shared-state cache" and is controlled with the SSTATE_DIR variable in your local.conf.
• Set the BB_NUMBER_THREADS and PARALLEL_MAKE variables in your local.conf to match your machine's resources. These variables control how many tasks are run in parallel and how many processes 'make' should run in parallel (-j option) respectively.
• Put the 'build' directory on its own disk.
• Use the ext4 filesystem without journaling and with these mount options: noatime,barrier=0,commit=6000. WARNING: This makes your hdd unreliable in case of power losses. Do not store anything of value on this hdd.
• building images with -dev and/or -dbg packages increases the do_rootfs task time considerably. Make sure you enable them (see EXTRA_IMAGE_FEATURES in your local.conf) only when needed.
• openembedded and yocto both support icecream (distributed compile). See the icecc class and this post.
• Buy a faster machine ;)

References:

Yocto Build Performance Wiki

Bitbake GUI tools