Re: On K7, -march=k6 is good (Was Re: Why no -march=athlon?)

[Benoit Poulot-Cazajous <Benoit.Poulot-Cazajous@Sun.COM>]

"M. R. Brown" <mrbrown@0xd6.org> writes:

> * Benoit Poulot-Cazajous <poulot@ifrance.com> on Wed, Dec 19, 2001:
> 
> > 
> > But gcc-2.95,x _supports_ "-march=k6", and we should use that instead of
> > "-march-i686".
> > 
> 
> No, k6 != athlon.  IIRC, the i686 optimization is closer to the Athlon than
> the k6 opt.

In theory, you may be right. But gcc-2.95.3 may not follow the theory.

> > before the patch :
> > 1017.92user 261.80system 24:39.89elapsed 86%CPU
> > 706.33user 160.79system 16:23.61elapsed 88%CPU
> > 1787.38user 418.76system 43:35.97elapsed 84%CPU
> > 
> > after the patch :
> > 1018.42user 253.85system 24:44.68elapsed 85%CPU
> > 704.89user 151.76system 16:16.14elapsed 87%CPU
> > 1786.96user 410.76system 43:05.32elapsed 85%CPU
> > 
> > The improvement in system time is nice.
> > 
> 
> Er, there's not much difference...

>From 261.80 to 253.85 => -3%
>From 160.79 to 151.76 => -6%
>From 418.76 to 410.76 => -2%

So the kernel looks between 2 and 6% faster. Not so bad for a one-line
patch ;-)

> Curious, what happens when you compile using gcc 3.0.1 against
> -march=athlon?

Yep, I will try with gcc 3.0.3.

  -- Benoit