lkml.org 
[lkml]   [2004]   [Oct]   [30]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
/
DateSat, 30 Oct 2004 18:43:21 -0700 (PDT)
FromLinus Torvalds <>
SubjectRe: Semaphore assembly-code bug

On Sun, 31 Oct 2004, Andi Kleen wrote:
> 
> Using the long stack setup code was found to be a significant
> win when enough registers were saved (several percent in real benchmarks) 
> on K8 gcc. 

For _what_?

Real applications, or SpecInt?

The fact is, SpecInt is not very interesting, because it has almost _zero_
icache footprint, and it has generally big repeat-rates, and to make
matters worse, you are allowed (and everybody does) warm up the caches by
running before you actually do the benchmark run.

_None_ of these are realistic for real life workloads. 

>  It speed up all function calls considerably because it 
> eliminates several stalls for each function entry/exit. 

.. it shaves off a few cycles in the cached case, yes.

> The popls will all depend on each other because of their implicied
> reference to esp.

Which is only true on moderately stupid CPU's. Two pop's don't _really_ 
depend on each other in any real sense, and there are CPU's that will 
happily dual-issue them, or at least not stall in between (ie the pop's 
will happily keep the memory unit 100% busy).

		Linus
-
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: 2005-03-22 14:07    [from the cache]
©2003-2008