Re: Regarding performance issues with the Emacs 25.1 Windows-build

[Eli Zaretskii]

> From: Jostein Kjønigsen <address@hidden>
> Date: Wed, 09 Nov 2016 09:34:05 +0100
> 
> https://www.reddit.com/r/emacs/comments/598iot/on_windows_emacs_251_is_noticeably_slower_than/
> 
> The numbers here show Emacs 25.1 on Windows to be almost twice as slow
> as 24.5!

My measurement show only a very mild slowdown, about 20% to 30%.
Nowhere near twice slower.  The last timing in the benchmark posted to
reddit is actually twice _faster_ with Emacs 25.1.

FWIW, I don't feel any slowdown in day-to-day usage of Emacs, which is
consistent with the above measurements.

The only significant change in Emacs 25.1 on Windows is how we
allocate memory, AFAIR.  However, the posted benchmark doesn't
allocate any significant memory, AFAICT.

> How was the Windows-version built? Was it built by the same people,
> using the same setup and the same toolchain? Or was something done
> differently this time?

The answer is probably that it was not built the same, but I very much
doubt that the differences could explain a twofold performance hit.

FWIW, my binaries were built by myself using the same compilation
options (-O2 optimization), but I upgraded my compiler from GCC 4.8.1
to 5.3.0 between the two versions of Emacs.  Again, I very much doubt
that this could explain any significant performance differences.

> Anyone have idea how we can go about this fixing this?

The first step is to identify which part(s) are now slower.