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Re: Bootstrap times on mainline are getting worse
- From: Zack Weinberg <zack at codesourcery dot com>
- To: Roger Sayle <roger at eyesopen 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 11:10:56 -0700
- Subject: Re: Bootstrap times on mainline are getting worse
- References: <Pine.LNX.firstname.lastname@example.org>
On Sat, Oct 19, 2002 at 11:25:55AM -0600, Roger Sayle wrote:
> 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.
Yeah, I wrote this before I saw your message.
I still think it's worth shrinking processor_costs - we're getting
nickled and dimed to death on cache utilization, and this is a cheap
way to get quite a bit of space back.
> 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....
The only thing that's really gone up is the integer divide cost. Even
load/store costs are stable in the 2-16 cycles range (presumably this
is cost to fetch from L1 cache). I'd wait until we really do have a
cost above 256 and then change just that one entry to unsigned short.