Re: BASE_PURESIZE

[Eli Zaretskii <eliz@gnu.org>]

> From: Andreas Schwab <schwab@linux-m68k.org>
> Cc: emacs-devel@gnu.org
> Date: Sat, 24 Oct 2009 12:37:19 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > For the record, the extra use of purecopy caused the pure_bytes_used
> > value to go up by 52KB on 32-bit Windows, and by 92KB on 64-bit
> > GNU/Linux.  So it looks like the ratio is actually closer to 9/5 than
> > to either the old 10/6 or the new 11/7.  Or maybe I'm missing
> > something.
> 
> It all depends on the ratio of string data vs. lisp object pure storage.

I made some measurements.  The ratio of 11/7 seems to work pretty
well, but there are two additional problems:

 . The default value of SYSTEM_PURESIZE_EXTRA is zero, and is not
   increased for GUI builds.  This causes a --without-x build to waste
   some 100KB.  If we want to handle this, the basic constant in
   BASE_PURESIZE can be as low as 1290000 and SYSTEM_PURESIZE_EXTRA
   should have its default at 140000 for GUI builds, zero otherwise.

 . The amount of pure storage used by load-history depends on the
   length of the filename of the directory where Emacs is dumped.  In
   my case, I have 32 characters before the "emacs/lisp/" part, so I'm
   guessing that's the main reason the value of 1430000 was too small
   for me.

We could decide that we don't care too much about the --without-x
case, but what about the second problem?  If we want to handle it
without wasting storage on systems with shorter file names, we would
need some code in src/Makefile.in that would measure the length of the
directory name and enlarge PURESIZE accordingly.