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)...
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.
Later,
David S. Miller
davem@redhat.com
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