Re: [Valgrind-developers] valgrind: r5362 - trunk/perf

[Julian S. <js...@ac...>]

On Monday 19 December 2005 17:25, Nicholas Nethercote wrote:
> On Sat, 17 Dec 2005, Julian Seward wrote:
> >>>> P4 Northwood (suse10, x86):
> >>>> heap     trunk     : 0.4s  nl: 5.7s (12.9x, -----)  mc:85.8s (195.0x,
> >>>> -----)
> >>
> >> I did the same yesterday and saw similar things.  The counts in swizzle
> >> just don't add up to the function totals.
> >
> > Nevertheless, as usual cachegrind does a great job of pointing out the
> > smoking gun.  Run time of this program is literally halved following
> > r5365.
>
> I get a 25% speedup.  I tried a couple of real programs (konqueror, vim)
> but don't see any effect on them.  Still, it can't have hurt.

I'm getting the impression that the cache-related performance problems
we've identified recently exist on all platforms, but are most pronounced 
on older P4s, due to the high clock rate, small D1 (8k) and small L2 (256k).
There was also a small change in starting a real program (ktuberling), 95 to
93 seconds.

On a Mac Mini, which has more generous cache arrangements, I saw a change
from a 47x slowdown to 33x, IIRC.  I suspect that's more typical.

J