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SubjectRe: [PATCH] remove zone_mem_map
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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