Re: [patch] arch hook for notifying changes in PTE protections bits

[David S. Miller]

On Sat, 19 Mar 2005 12:30:05 -0800
David Mosberger <davidm@xxxxxxxxxxxxxxxxx> wrote:

> I agree about your concern about cost.  Accessing the page_map is
> expensive (integer division + memory access) and we have to do that in
> order to find out if the page is i-cache clean.

First, it's a multiply by reciprocol.  At least on sparc64 I get
this emitted by the compiler.

Secondly, if you're willing to sacrifice 8 bytes per page struct
simply define WANT_PAGE_VIRTUAL and page struct will be exactly
64 bytes and thus the divide a will turn into a simple shift.
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