[Scons-users] SCons very slow on GitHub actions

[Leonard de Ruijter]

Dear Mats,


Thanks for your quick reply.

You can find comparison times in 
https://github.com/LeonarddeR/scons-examples/actions/runs/14706591575

This uses the workflow file found in 
https://github.com/SCons/scons-examples/pull/7

As you can see here, the Ubuntu and Mac runs take around 7 seconds, 
whereas the Windows runs take over a minute. The builds run with 
--debug=time, so you can see from the build steps that the reading part 
of the execution takes around 54 seconds.


Regards,


Leonard

On 4/28/2025 3:33 PM, Mats Wichmann wrote:
> On 4/28/25 06:03, Leonard de Ruijter wrote:
>> Hello,
>>
>> I'm suffering from very slow SCons script reading times on Github 
>> Actions with Windows runners. For an example, see https://github.com/ 
>> LeonarddeR/scons-examples/actions/runs/14706591575/job/41268375471
>>
>> Things I've tried so far to fix this are:
>> - Pinned version of Python with the setup-python action, both X86 and 
>> X64
>> - Pinned version of SCons to an older version, e.g. 4.8.1
>> - Server 2025 image
>> - Run in a venv with uv
>> - Cleaning up the path variable, since it is known to be full of 
>> garbage on GH Actions
>> - Using a Windows dev drive
>>
>> There's definitely a variable on Github Actions that kicks us here, 
>> but apart from the script reading phase, all seems pretty smooth 
>> afterwards. And not to mention that other runners are going fine.
>>
>> Kind regards,
>>
>> Leonard de Ruijter
> Hard to say too much at this point. How slow is it? Do you have a 
> comparison to, say, a Linux build? Are there a lot of files involved 
> in building the dependency tree? Do they result in a lot of work 
> (dependency scanning, etc.)?
>
> The contents of PATH shouldn't affect times since SCons ignores it. 
> Are you by any chance importing PATH in your build?
>
> SCons *is* slower on Windows. It's irritating to those of us who run 
> the test suite a lot, because where Windows is demonstrably slower is 
> in the plumbing of creating a new process. That hurts the test suite 
> because we do it over and over again - 1200+ tests run scons 1-3 times 
> each, and many of those have command actions which spawn further 
> processes, so it adds up. The GH Actions runs of our test suite take 
> 5:45 on Linux, 17m+ on Windows. However... that usually isn't a big 
> factor building a single project, and you'd see it in the build phase, 
> not in the reading phase.
>
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