Martin Dalecki <dalecki@evision-ventures.com> said:
> Well it's kind like the answer to the question: why don't do it all in hand
> optimized assembler? Or in other words - let's give the GCC guys good
> reasons for more hard work. But more seriously:
>
> Things like unlikely() tricks and other friends seldomly really
> pay off if applied randomly. But they can:
>
> 1. Have quite contrary effects to what one would expect due to
> the fact that one is targetting a single instruction set but in
> reality multiple very different CPU archs or even multiple archs.
>
> 2. Changes/improvements to the compiler.
>
> My personal rule of thumb is - don't do something like the
> above unless you did:
>
> 1. Some real global profiling.
> 2. Some real CPU cycle counting on the micro level.
> 3. You really have too. (This should be number 1!)
Anybody trying to tune code should read (and learn by heart):
@Book{bentley82:_writing_eff_progr,
author = {Jon Louis Bentley},
title = {Writing Efficient Programs},
publisher = {Prentice Hall},
year = 1982
}
(sadly out of print AFAIK)
-- Dr. Horst H. von Brand User #22616 counter.li.org Departamento de Informatica Fono: +56 32 654431 Universidad Tecnica Federico Santa Maria +56 32 654239 Casilla 110-V, Valparaiso, Chile Fax: +56 32 797513- 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/
This archive was generated by hypermail 2b29 : Fri Jun 07 2002 - 22:00:21 EST