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Re: GCC 4.1: Buildable on GHz machines only?
- From: "H. J. Lu" <hjl at lucon dot org>
- To: Joe Buck <Joe dot Buck at synopsys dot COM>
- Cc: Andrew Haley <aph at redhat dot com>,Alexandre Oliva <aoliva at redhat dot com>,David Edelsohn <dje at watson dot ibm dot com>, Andreas Schwab <schwab at suse dot de>,Richard Earnshaw <rearnsha at gcc dot gnu dot org>,Andrew Pinski <pinskia at physics dot uc dot edu>,Paul Koning <pkoning at equallogic dot com>, s dot bosscher at student dot tudelft dot nl,gcc at gcc dot gnu dot org, matt at 3am-software dot com, cow at compsoc dot man dot ac dot uk
- Date: Wed, 4 May 2005 09:17:19 -0700
- Subject: Re: GCC 4.1: Buildable on GHz machines only?
- References: <jebr7z80nt.fsf@sykes.suse.de> <17009.2368.986169.753001@cuddles.cambridge.redhat.com> <200504281609.j3SG9ZD27524@makai.watson.ibm.com> <20050428164727.GB30649@synopsys.com> <200504281654.j3SGs0D27158@makai.watson.ibm.com> <oracncw0a1.fsf@livre.redhat.lsd.ic.unicamp.br> <20050503220342.GA23969@synopsys.com> <17016.41624.799846.161219@cuddles.cambridge.redhat.com> <20050504134157.GA5261@lucon.org> <20050504160005.GB26103@synopsys.com>
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.