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Re: Bootstrap times on mainline are getting worse
- From: Roger Sayle <roger at eyesopen dot com>
- To: Zack Weinberg <zack at codesourcery dot com>
- Cc: <gcc at gcc dot gnu dot org>, <gcc-patches at gcc dot gnu dot org>, Diego Novillo <dnovillo at redhat dot com>
- Date: Sat, 19 Oct 2002 11:25:55 -0600 (MDT)
- Subject: Re: Bootstrap times on mainline are getting worse
Hi Zack,
> > A 'time make bootstrap' on version "2002-10-03" gives:
> >
> > real 57m38.632s
> > user 51m20.200s
> > sys 4m55.500s
> >
> > With this patch I get:
> >
> > real 58m16.766s
> > user 51m14.720s
> > sys 5m0.850s
>
> I smell cache blowout. Notice how the real and system times went up,
> but the user time went down?
I think that you're barking up the wrong tree on this one. As I've
mentioned in http://gcc.gnu.org/ml/gcc/2002-10/msg01183.html, we're
still looking for a 6% (approx 4 minute slow-down) around October 5th.
Total process times above, 56m:15.7 before and 56m:15.5 after showed
that this patch itself had virtually no effect. The minor difference
in wall clock times can easily be explained by attributed to other
processes running on the same machine.
Also be carefull about changing these RTX costs to unsigned char.
Pentium4 already has integer division costs at around 120, and
improvements in superscalar issue vs memory latency could easily
push values above 256 on x86 within only a year or so. Just look
at the curves for i386, i486, pentium, pentiumpro, pentium4....
Roger
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