Speeding up ggc-simple on stage1

[Jeffrey A Law]

  In message < orbt6oykn5.fsf@garnize.lsd.ic.unicamp.br >you write:
  > > Presumably that host can't use gcc-page?
  > 
  > Yep.  configure claims the platform doesn't support mmap nor valloc :-(
Actually, I've found valloc is not a good thing either.  It effectively
doubles the amount of memory we need if I remember correctly.  I just never
got around to writing up a report on that and asking for suggestions about
what to do :-)

  > > Yes, ggc-simple is painfully slow.  It took several days to
  > > bootstrap an m68k box I've got access to using gcc-simple.
  > 
  > Well, the unoptimized stage1 cc1 has been trying to build tree.c for
  > the past 24 hours or so :-(
  > 
  > Nevertheless, `ps' says it's used just 54 minutes of CPU.  So it looks
  > like the system is thrashing, which is not that surprising, given that
  > it's got just 16MB of memory :-( :-(
Yea, you're thrashing.  The only aspect of this change that might help that
is a smaller call chain within the garbage collector.

Another way to test it would be to use ggc-simple on a more beefy box
(there's a configure option to tweak the garbage collection selection).

  > > Not without at least knowing it's an improvement.  I'm not talking about
  > > a massive study of its performance.  Build cc1 with and without this
  > > change and run a substantial file through the compiler.
  > 
  > Should it be an optimized or unoptimized cc1?  Can it be cc1 from
  > stage1, built with gcc 2.95.2?
Your choice.  If it's an improvement I'd expect it to show up regardless of
those issues.


jeff