On Fri, Jan 12, 2007 at 09:59:40AM +0000, Alan wrote: > On Fri, 12 Jan 2007 07:02:13 +0100 > Nick Piggin <[EMAIL PROTECTED]> wrote: > > > Just noticed this while looking at a bug. > > Avoid an expensive integer divide 3 times per CPU per tick. > > Integer divide is cheap on some modern processors, and multibit shift > isn't on all embedded ones.
Well integer divide unit is non-pipelined on P4 K8 Core2 and probably most processors, AFAIK. So the 3 divs would take 240 cycles on a P4, perhaps. > How about putting back scale = 1 and using > > scale += scale; > > instead of the shift and getting what ought to be even better results Yes I gues we ccan do this as well, good idea. I'll make a quick userspace benchmark and post some numbers with my next submission. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
