Re: [PATCH] rmap 13a

[William Lee Irwin III <wli@holomorphy.com>]

On Wed, May 08, 2002 at 08:21:37PM +0200, Roman Zippel wrote:
> I'd suggest, we move page_address to asm/page.h (as counterpart of
> virt_to_page). discontigmem configs can then use some more efficient
> table lookup. Other config usually want to implement it better as:
> #define page_address(page)	((((page) - mem_map) << PAGE_SHIFT) +
> PAGE_OFFSET)
> bye, Roman

Sorry, I missed the part about table lookup.

If table lookup is wanted, I feel that should also be a generic option.
There is nothing inherently architecture-specific about using a table-
driven method of calculating page_address().

But why isn't zone_table[] already an instance of such a table?

An annotated description of the generic version is:

/* the table lookup */    
zone = zone_table[page->flags >> ZONE_SHIFT]

     /* the phys offset of the table entry */
__va(zone->zone_start_paddr
         +
/* calculating the offset within the table region */   /* scaling the offset */
((page - zone->zone_mem_map)                                << PAGE_SHIFT))



Cheers,
Bill
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