On Thu, Dec 28, 2000 at 03:14:56PM -0800, David S. Miller wrote:
> Date: Fri, 29 Dec 2000 00:17:21 +0100
> From: Andi Kleen <ak@suse.de>
>
> On Thu, Dec 28, 2000 at 02:54:52PM -0800, David S. Miller wrote:
> > To make things like "page - mem_map" et al. use shifts instead of
> > expensive multiplies...
>
> I thought that is what ->index is for ?
>
> It is for the page cache identity Andi... you know, page_hash(mapping, index)...
Oops, I confused it with the 2.0 page->map_nr, which did exactly that.
I should have known better. Thanks for correcting this brainfart.
> And the add/sub/shift expansion of a multiply/divide by constant even
> in its' most optimal form is often not trivial, it is something on the
> order of 7 instructions with waitq debugging enabled last time I
> checked.
Wonder if it looks better with wq debugging turned off or a compressed
->zone.
-Andi
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