Messages in this thread | | | Date | Fri, 29 Dec 2000 00:17:21 +0100 | From | Andi Kleen <> | Subject | Re: test13-pre5 |
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On Thu, Dec 28, 2000 at 02:54:52PM -0800, David S. Miller wrote: > Date: Thu, 28 Dec 2000 23:58:36 +0100 > From: Andi Kleen <ak@suse.de> > > Why exactly a power of two ? To get rid of ->index ? > > To make things like "page - mem_map" et al. use shifts instead of > expensive multiplies...
I thought that is what ->index is for ?
Also gcc seems to be already quite clever at dividing through small integers, e.g. using mul and shift and sub, so it may not be even worth to reach for a real power-of-two.
I suspect doing the arithmetics is at least faster than eating the cache misses because of ->index.
-Andikkk
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