Re: Bootstrap times on mainline are getting worse

[Zack Weinberg <zack at codesourcery dot com>]

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.

zw