Speeding up ggc-simple on stage1

Alexandre Oliva oliva@lsd.ic.unicamp.br
Fri Jan 14 03:09:00 GMT 2000

On Jan 14, 2000, Jeffrey A Law <law@cygnus.com> wrote:

>> Unfortunately, I've got a
>> slow powerpc running AIX 4.1 (it won't run GNU/Linux :-(, that takes
>> ages to build stage2 and, it seems that, whenever I attach gdb to cc1,
>> it's within running garbage collection code :-(

> Presumably that host can't use gcc-page?

Yep.  configure claims the platform doesn't support mmap nor valloc :-(

> 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 :-( :-(

>> I believe reducing stack usage for garbage collection could help it
>> some, so I've tried to rewrite some (all?) of the recursive functions
>> in ggc-simple to try to avoid recursion as much as possible.  I can't
>> say that know it's fast, but it seems to have improved a bit.

> I'd like to know that we're actually going to improve things before we
> start making changes.

Sounds reasonable.

>> Is this ok to install?

> 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?

> combine.i, reload.i or reload1.i are always good candidates for this
> kind of test.

Ok.  I hope I can obtain some results before the end of Y2K :-) :-)

> You also have some formatting problems.

Oops, sorry, thanks for pointing it out (again :-(.

It's really hard to get rid of old habits :-)

Alexandre Oliva http://www.ic.unicamp.br/~oliva IC-Unicamp, Bra[sz]il
oliva@{lsd.ic.unicamp.br,guarana.{org,com}} aoliva@{acm,computer}.org
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