We have detected a build metrics regression from push:

https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=2ce7f6ee895d9ac8207a64c95632c62e7d3c7b46&tochange=29582b2a7db1f46fd30d47769a965d9c693a2019

As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

12% build times windows2012-64 debug rusttests taskcluster-c5.4xlarge 433.57 -> 484.09
11% build times windows2012-32 debug rusttests taskcluster-c5.4xlarge 432.33 -> 479.96
8% build times windows2012-32 debug rusttests taskcluster-c4.4xlarge 572.66 -> 619.13

You can find links to graphs and comparison views for each of the above tests at: https://treeherder.mozilla.org/perf.html#/alerts?id=20149

On the page above you can see an alert for each affected platform as well as a link to a graph showing the history of scores for this test. There is also a link to a treeherder page showing the jobs in a pushlog format.

To learn more about the regressing test(s), please see: https://developer.mozilla.org/en-US/docs/Mozilla/Performance/Automated_Performance_Testing_and_Sheriffing/Build_Metrics

*** Please let us know your plans within 3 business days, or the offending patch(es) will be backed out! ***

Hmm, I would've expected that to improve build-times if anything, though we're building a bit more code after all... Does this only affect rusttests? Or other builds as well?

(In reply to Emilio Cobos Álvarez (:emilio) from comment #1)

Hmm, I would've expected that to improve build-times if anything, though we're building a bit more code after all... Does this only affect rusttests? Or other builds as well?

This only affects rusttests, debug & opt builds on Windows 32 & 64 bit architectures.

I've been investigating some build times increases on Linux for some days now. Seems like they're also related to this issue,
as they happened at pretty much the same time.

Regressions:

7% build times linux64 opt base-toolchains-clang taskcluster-c4.4xlarge 1,850.27 -> 1,977.77
7% build times linux64 opt base-toolchains-clang taskcluster-m5d.4xlarge 1,624.69 -> 1,734.26
3% build times linux64 opt base-toolchains-clang taskcluster-c5.4xlarge 1,661.81 -> 1,715.92

(In reply to Ionuț Goldan [:igoldan], Performance Sheriffing from comment #2)

(In reply to Emilio Cobos Álvarez (:emilio) from comment #1)

Hmm, I would've expected that to improve build-times if anything, though we're building a bit more code after all... Does this only affect rusttests? Or other builds as well?

This only affects rusttests, debug & opt builds on Windows 32 & 64 bit architectures.

So I'm updating this list with Linux opt builds on base-toolchains-clang.

:emilio any plans to fix this in the future?

No, this only affected unit tests that are not regularly built by developers, only on windows, and should've improved build times elsewhere.