Re: Emacs build times on Windows

[Christoph Scholtes <cschol2112@googlemail.com>]

Hi Eli,

On 4/21/2012 1:29 AM, Eli Zaretskii wrote:

> On my i7 desktop (4 hyper-threaded cores), it takes 9 minutes, if I
> use the -j10 switch to Make.  I suggest that you try -j6 in your
> builds (if you use anything older than the current CVS of GNU Make,
> you will also have to use the XMFLAGS="-j6" kludge as well, see
> nt/INSTALL).  A parallel build should be faster.

Thanks. Does this work with mingw32-make also or do I have to use Cygwin 
(or MSYS?) to obtain gmake?

I tried building with mingw32-make -j2 but it did not result in any 
significant speedup.

> The extra build with a large PURESIZE is not the problem.  Each one of
> the 2 compilations of the Emacs sources takes 20 seconds on my machine
> (using "make -j10"), which is negligibly short compared to the
> compilation of Lisp files.  ("make -j10 info" takes another 5 seconds,
> but only on the trunk, where I recently made the 'info' target of
> nt/makefile.w32-in more parallel-friendly.)

On my system the extra PURESIZE build takes a lot longer than 20 
seconds, but hopefully I can reduce that by using parallel compilation.

> Very simple: the byte compilation on Posix platforms can run in
> parallel, because it uses a generic .el.elc rule.  By contrast, on
> Windows we compile them sequentially, one after the other, because the
> recipe says:
>
>    compile-CMD:
>    #	-for %%f in ($(lisp) $(WINS)) do for %%g in (%%f\*.elc) do @attrib -r %%g
> 	  for %%f in ($(COMPILE_FIRST)) do \
> 	    $(emacs) -l loaddefs $(BYTE_COMPILE_FLAGS) -f batch-byte-compile-if-not-done %%f
> 	  for %%f in (. $(WINS)) do for %%g in (%%f/*.el) do \
> 	    $(emacs) -l loaddefs $(BYTE_COMPILE_FLAGS) -f batch-byte-compile-if-not-done %%f/%%g
>
> IOW, we use a shell-level loop to compile the files one by one.
>
> So if you are looking for the place to significantly speed up the
> bootstrap, the first place to look is to make the byte compilation use
> a similar setup to what you see in lisp/Makefile.in.

I see. I will look into that. Thanks.

Christoph