Re: [PATCH] remove zone_mem_map

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

Christoph Lameter wrote:
> On Wed, 22 Feb 2006, KAMEZAWA Hiroyuki wrote:
>
> > This patch removes zone_mem_map.
>
> Note that IA64 does not seem to depend on zone_mem_map...
Oh, yes. ia64 doesn't includes asm-generic/memory_model.h when DISCONTIGMEM.

> > Index: test/include/asm-generic/memory_model.h
> > ===================================================================
> > --- test.orig/include/asm-generic/memory_model.h
> > +++ test/include/asm-generic/memory_model.h
> > @@ -47,9 +47,9 @@ extern unsigned long page_to_pfn(struct
> >
> >  #define page_to_pfn(pg)			\
> >  ({	struct page *__pg = (pg);		\
> > -	struct zone *__zone = page_zone(__pg);	\
> > -	(unsigned long)(__pg - __zone->zone_mem_map) +	\
> > -	 __zone->zone_start_pfn;			\
> > +	struct pglist_data *__pgdat = NODE_DATA(page_to_nid(__pg));	\
> > +	(unsigned long)(__pg - __pgdat->node_mem_map) +	\
> > +	 __pgdat->node_start_pfn;			\
> >  })
>
> NODE_DATA is an arch specific lookup, If it always is a table lookup
> then the performance will be comparable to page_zone because that also 
> involves one table lookup.
There are several types of NODE_DATA definitions.
1. #define NODE_DATA(node)	(&node_data[node]) alpha,arm,
2. #define NODE_DATA(node)      (node_data[node]) i386,powerpc,x86_64,m32r
3. #define NODE_DATA(node)	(&node_data[node]->pgdat) parisc,mips
4. #define NODE_DATA(node)	(per-cpu-page has node_data[nid] pointer array) ia64

BTW, ia64 looks very special. Does it make sensible performance gain ?

-- Kame

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