Re: 2.6.13/14 x86 Makefile - Pentiums penalized ?

[Chris White <chriswhite@gentoo.org>]

On Tuesday 13 September 2005 15:04, Margit Schubert-While wrote:
> In arch/i386/makefile we have :
> cflags-$(CONFIG_MPENTIUMII)     += -march=i686 $(call
> cc-option,-mtune=pentium2)
> cflags-$(CONFIG_MPENTIUMIII)    += -march=i686 $(call
> cc-option,-mtune=pentium3)
> cflags-$(CONFIG_MPENTIUMM)      += -march=i686 $(call
> cc-option,-mtune=pentium3)
> cflags-$(CONFIG_MPENTIUM4)      += -march=i686 $(call
> cc-option,-mtune=pentium4)
>
> According to the gcc 3.x doc, the -mtune is not avaliable for i686
> and, indeed, with 3.3.5 no -mtune is generated/used (make V=1).

That's correct, gcc 3.4 started the -mtune flag.  Chances are if you really 
want the -mtune optimizations you're going to have to upgrade to gcc 3.4 or 
greater.

> This, of course, heavily penalizes P4's (the notorious inc/dec).

Are you referring to cpu cycle counts?  Is there certain code that causes the 
kernel to perform that unfavorably by a large scale?

> Margit

Chris White

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