[Scons-dev] scons-2.5.0 performance issue?

[Bill Deegan]

Thomas,

Can you run and post with "--debug=count"?

Thanks,
Bill

On Mon, Apr 11, 2016 at 7:14 AM, Thomas Berg <merlin66b at gmail.com> wrote:

> Hi all,
>
> First of all, thanks for the 2.5.0 release!
>
> I have tested it in the build at my dayjob now, where we have a large
> C++ application built with scons: around 7-8000 .cpp files, same
> amount of headers, some code generation steps including Qt moc-ing.
> Unfortunately it seems that something has happened in scons-2.5.0 that
> slows down the no-op build quite significantly. This is the output of
> scons --debug=time in an almost-no-op build of our source tree:
>
> ========================================================
> = 2.5.0
> ========================================================
>
> Total build time: 933.582000 seconds
> Total SConscript file execution time: 55.395000 seconds
> Total SCons execution time: 858.109000 seconds
> Total command execution time: 20.078000 seconds
>
> ========================================================
> = 2.4.1
> ========================================================
>
> Total build time: 337.473000 seconds
> Total SConscript file execution time: 62.303000 seconds
> Total SCons execution time: 256.638000 seconds
> Total command execution time: 18.532000 seconds
>
> ========================================================
> = 2.3.4
> ========================================================
>
> Total build time: 331.774000 seconds
> Total SConscript file execution time: 61.290000 seconds
> Total SCons execution time: 249.606000 seconds
> Total command execution time: 20.878000 seconds
>
> ------------------------------------------------------------
> This is with python-2.7.9 64bit on Windows 7.
>
> So it seems that the scons execution time has increased by a factor of
> 3 in our build, between scons-2.4.1 and 2.5.0 :(
>
> For us the 5.5 minute no-op build time has already been an issue, so
> the new 15 minute no-op build is bad news. If you have just changed a
> single file, and need to build from the top to check that everything
> is up to date, 15 minutes is a very long time... I'm seeing similar
> slowdowns for our partial builds where we only execute some of our
> SConscripts (build time going from 16 to 25 seconds for example).
>
> 1. Is anyone else seeing this?
> 2. Any idea what changes that could cause something like this? I could
> try bisecting or reverting some changes to narrow it down
> 3. Is there anything else I can do, like posting the output of profiling?
>
> I also have some other smaller hobby C++ projects that I could profile.
>
> Thanks for any hints,
> Thomas Berg
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