Messages in this thread | | | Subject | Re: 2.5.20 RAID5 compile error | Date | Tue, 04 Jun 2002 14:22:21 -0400 | From | Horst von Brand <> |
| |
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/
| |