Re: Two strange messages while building Emacs on MS-Windows

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 12 Dec 2012 05:48:51 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: monnier@iro.umontreal.ca, emacs-devel@gnu.org
> 
> > Date: Tue, 11 Dec 2012 22:58:33 +0100
> > From: Dani Moncayo <dmoncayo@gmail.com>
> > Cc: monnier@iro.umontreal.ca, emacs-devel@gnu.org
> > 
> > > As expected.  So, if compiling the C sources takes 1 min and compiling
> > > the Lisp files takes 6.5 min, how come the bootstrap takes 15 min?
> > > What else takes 7.5 min?
> > 
> > I don't know.  It seems that a bootstrap is not equivalent to the sum
> > of the two commands we've measured.
> 
> The only other thing is deleting files at the beginning of bootstrap.
> 
> I suggest to bootstrap with a clock in your hand, and make notes about
> the times each part takes.  There are at least 5 min more to gain
> here, so I think you should be motivated enough ;-)

This is a bit longish message, sorry.  The bottom line is that I think
I know where those 5 min come from, and that Dani should get used to
the 15-min mark for the time being.

First, on my Core i7 running XP, and with "make -j8", the detailed
time schedule of a full bootstrap are:

  1:10 min for the initial compilation of C sources
  0:30 min for generating loaddefs
  4:10 min for compiling Lisp files
  0:26 min for the final compilation of C sources
  6:46 min total

After the bootstrap, removing all the *.elc files and recompiling them
with emacs.exe, which includes a byte-compiled byte compiler, takes
about 2:30 to 3 min with "make -j8", which is 60% of the time it takes
using an interpreted byte compiler.  Not the 25% I somehow measured a
day or two ago.

I also did measurements on a Windows 7 machine.  This one has a Core 2
duo E7300 CPU, so it is slightly less powerful than what Dani has.
Here's the bootstrap schedule on that machine using "make -j2":

  1:45 min for the initial compilation of C sources
  0:50 min for generating loaddefs
 11:35 min for compiling Lisp files
  0:50 min for the final compilation of C sources
 16:00 min total

Removing *.elc files and recompiling all of them with byte-compiled
compiler and "make -j2" takes 6:00 minutes, which is again almost
twice faster.  IOW, the missing 5 min are the difference between
compiling Lisp files with an interpreted byte compiler and a
byte-compiled one.

So I guess the 15 min that Dani gets is what is possible on a 2-core
machine, and any further improvements are possible only if Emacs is
re-dumped with byte-compiled preloaded filed early on and then that
binary used to compile the rest of Lisp files, like we do on Unix.