eon performance regression

[Paolo Carlini]

Andreas Jaeger wrote:

> > I have a couple of naive questions:
> > 1- Which compile flags are used for peak and base?
>
> Base flags: -O2 -march=athlon -malign-double
>   Peak flags: -O3 -fomit-frame-pointer -march=athlon
>   (cont.)     -funroll-all-loops -fstrict-aliasing
>   (cont.)     -malign-double
>   To compile and execute eon correctly the following extra flags
>   are used for compilation: -ffast-math -fwritable-strings.
>
> for more details, check e.g.:
> http://www.suse.de/~aj/SPEC/CINT/sandbox-b/200112291813.int/CINT2000.354.html

Thank you very much.
Sorry for having asked those information when they are in fact readily available on
that WEB page.

> > 2- Does eon use std::string? Is it I/O bound (on the concerned architecture)?
>
> I don't think so, a grep for "std::string" revealed no matches.  eon
> is old and can even be compiled with gcc 2.95.x
>
> eon is not I/O bound.  All SPECcpu tests should be memory and CPU
> bound only.

As I expected...

> > (I'm asking this because among the libstdc++ patches one affects only the former,
> > the other only the latter functionality)
>
> Strange.

... really!

Andreas, honestly, I think there is very feeble evidence that those libstdc++ patches
are really responsible for the slow down Jan's noticed from that date. What do you
think?

More generally, do you think is likely that a *very* high level libstdc++ change
manifest itself as a performance regression only on the peak and not in the base
benchmark?

Cheers,
Paolo.