GCC 4.1: Buildable on GHz machines only?

[H. J. Lu]

On Wed, May 04, 2005 at 09:00:05AM -0700, Joe Buck wrote:
> On Wed, May 04, 2005 at 06:41:59AM -0700, H. J. Lu wrote:
> > On Wed, May 04, 2005 at 11:23:20AM +0100, Andrew Haley wrote:
> > > Joe Buck writes:
> > >  > Richard Henderson showed that the libjava build spends 2/3 of its time
> > >  > in libtool, and that his hand-hacked (but not portable) modification to
> > >  > invoke the appropriate binutils commands directly gave a huge speedup.
> > > 
> > > Yes, but please bear in mind that this *only* happens when you have a
> > > machine with huge RAM.  For other people with small RAM, the link
> > > itself is an important factor.  Also, other people have found that the
> > > libtool script consumes a smaller part of total execution time: rth's
> > > measurements are at one extreme of the scale.
> > 
> > We have been working on linker speed. If you have a number to show
> > that the GNU linker is very slow on certain things, I will take a
> > look.
> 
> I'm glad you're looking at speeding up the linker.  Please make sure to
> look at memory consumption as well, since performance falls off a cliff
> once the working set exceeds physical memory.  A good test would be to
> bootstrap gcc on a machine with 256M, or that is artificially limited to
> 256M (I seem to recall that you can tell a Linux kernel you have only a
> given amount of memory).

Given the current hardware, I would say 512MB is a reasonable number.
If I need to more than 256M to get 5% speed up, I will take it.

BTW, for gcc 4.0, I got

11687.92user 2089.89system 2:11:43elapsed 174%CPU (0avgtext+0avgdata
0maxresident)k

for bootstrap

9710.54user 2628.79system 1:52:03elapsed 183%CPU (0avgtext+0avgdata
0maxresident)k

for "make check" on a dual P3 550MHz with 512MB with everything except
for Ada.


H.J.