Fixed in Elixir main and v1.15 branches.
josevalim
Creator of Elixir
tosie
xpg
nhpip
So on the switch to R26 and 1.15.0 is faster for the most part, with the exception of unit tests. These are orders of magnitude slower to compile. One test in particular.
As a test I compiled using:
iex(cs@localhost)7> Kernel.ParallelCompiler.compile(["test/api/org_test.exs"], profile: :time)
Results for R25/1.14.2
[profile] 11588ms compiling + 0ms waiting for test/api/org_test.exs
[profile] Finished compilation cycle of 1 modules in 11589ms
[profile] Finished group pass check of 1 modules in 82ms
Results for R25/1.15.0
[profile] 213876ms compiling + 0ms waiting while compiling test/api/org_test.exs
[profile] Finished compilation cycle of 1 modules in 213876ms
[profile] Finished group pass check of 1 modules in 88ms
This is on a Mac (x86).
The test does a lot of creation of and matching of maps.
Continuing to debug.
So it appears to be a single test case that’s about 1500 lines long causing issues. Without that test:
[profile] 18699ms compiling + 0ms waiting while compiling test/api/org_test.exs
[profile] Finished compilation cycle of 1 modules in 18700ms
[profile] Finished group pass check of 1 modules in 33ms
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josevalim
Creator of Elixir
I have done a bug report to the OTP team about this. I am on my phone but you can check my submissions on the issues tracker. 
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josevalim
Creator of Elixir
Btw, if you can isolate that single test and share it, we can submit it upstream too as another example of the slow down.
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nhpip
linusdm
I’m investigating a bug related to gettext: Running `mix gettext.extract` doesn't extract new messages with Elixir 1.15 · Issue #367 · elixir-gettext/gettext · GitHub
It seems that the mix gettext.extract task doesn’t trigger a forced compilation anymore. It depends on a “trick” with making the compiler manifest file old (settings its change-date to the year 2000), and then running the “compile” or “compile.elixir” mix tasks.
When I try to emulate these steps, I see different behaviour in Elixir 1.14 vs 1.15. In both cases I first make the manifest file old (e.g. run touch -a -m -t 200001010000.00 _build/dev/lib/my_app/.mix/compile.elixir). The manifest file is located in _build/dev/lib/my_app/.mix/compile.elixir. And then I trigger a compilation with mix compile. With Elixir 1.14 a recompilation is triggered (I see the message Compiling 4 files (.ex)). While with Elixir 1.15 the same steps don’t trigger a compilation (no message is printed).
If this to be expected to work like this, I’d like to understand better how this changed from Elixir 1.14 to 1.15. Depending on the answer, the way to fix the aforementioned bug in gettext will be different.
Follow up: I’m suspecting this has something to do with this change: Store timestamps in manifests · elixir-lang/elixir@ce67dd6 · GitHub
I guess manipulating the last-modified date of the manifest file alone isn’t enough anymore, as there are now timestamps being stored in the manifest file itself.
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josevalim
Creator of Elixir
Elixir v1.15.1 has been released with fixes for the regressions reported here. Announcement: Elixir v1.15.1 released
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