lkml.org 
[lkml]   [2005]   [Sep]   [14]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
/
DateTue, 13 Sep 2005 23:48:22 -0700 (PDT)
FromZwane Mwaikambo <>
SubjectRe: 2.6.13/14 x86 Makefile - Pentiums penalized ?
On Wed, 14 Sep 2005, Chris White wrote:

> 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?

It's documented as being suboptimal to use inc/dec due to it modifying all 
of eflags resulting in dependency related stalls. add/sub only modifies 
one bit of eflags so is more optimal. However there is a problem of 
increased code size with add/sub.

But i've never benchmarked all of this ;)

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-09-14 08:44    [from the cache]
©2003-2008