Now in inbound, |mach build| will record *system* resource usage during
builds. You can later view the resource usage by running |mach
resource-usage| (mach will tell you at the end of the build if you can
run this).
The goal of this feature is to help people diagnose why builds are slow
and how builds are changing over time. You should be able to easily see
where CPU isn't at 100%, when I/O is slowing you down, when you are
swapping, etc. We should eventually be able to use this information to
tell you things like "your build could be faster if you had an SSD, more
memory, or more CPU cores." (We previously rolled out similar resource
monitoring to mozharness and hope to one day have builds and automation
producing the same machine readable data format so we can reuse the HTML
viewer to easily view resource usage of many different kinds of jobs.
The goal here is to identify poor hardware resource efficiency so we can
improve it.)
We only achieved the initial milestone by landing this feature. We still
have a lot of work to do. Bug 901601 tracks enabling this on non-mach
builds, which will start recording resource usage on automation
infrastructure. Bug 907297 tracks making the HTML display better. Bug
892342 tracks making the resource monitor more accurate. These will all
hopefully land in due time.
If you notice anything weird, please raise it in bug 883209 if it is
critical or file a follow-up in Core :: Build Config.
The HTML display is currently pretty poor. I'm not a good web developer
:) The HTML display is not part of the build, so I will rubber stamp
pretty much any patch that improves it. Please scratch your own itches!
Bug 907297 contains a list of suggested improvements.
For comparison purposes, [1] contains the output from a clobber build
with empty ccache on my MBP. As you can see, there are large chunks of
the build where we aren't CPU bound. Many of these are during recursive
make traversal, which is one reason we're focusing on moving away from
recursive make.
Finally, this is just a friendly reminder that if you build
mozilla-central and you don't have a machine with at least 4 *physical*
cores, 16 GB RAM, and an SSD, you should upgrade your hardware.
[1] https://people.mozilla.com/~gszorc/resources-references.png
Gregory
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