[PATCH] remove zone_mem_map

[PATCH] remove zone_mem_map

[KAMEZAWA Hiroyuki]

This patch removes zone_mem_map from zone.
By this, (generic) page_to_pfn and pfn_to_page can use the same logic.
This modifies page_to_pfn implementation. Could anyone do performance test on NUMA ?

(ia64 is not affected by this because it doesn't use generic page_to_pfn.)

-- Kame


This patch removes zone_mem_map.

However pfn_to_page uses pgdat, page_to_pfn uses zone.
page_to_pfn can use pgdat instead of zone, which is only one
user of zone_mem_map. By modifing it, we can remove zone_mem_map.


Signed-Off-By: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

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;			\
  })

  #elif defined(CONFIG_SPARSEMEM)
Index: test/include/linux/mmzone.h
===================================================================
--- test.orig/include/linux/mmzone.h
+++ test/include/linux/mmzone.h
@@ -225,7 +225,6 @@ struct zone {
  	 * Discontig memory support fields.
  	 */
  	struct pglist_data	*zone_pgdat;
-	struct page		*zone_mem_map;
  	/* zone_start_pfn == zone_start_paddr >> PAGE_SHIFT */
  	unsigned long		zone_start_pfn;

Index: test/mm/page_alloc.c
===================================================================
--- test.orig/mm/page_alloc.c
+++ test/mm/page_alloc.c
@@ -2117,7 +2117,6 @@ static __meminit void init_currently_emp
  	zone_wait_table_init(zone, size);
  	pgdat->nr_zones = zone_idx(zone) + 1;

-	zone->zone_mem_map = pfn_to_page(zone_start_pfn);
  	zone->zone_start_pfn = zone_start_pfn;

  	memmap_init(size, pgdat->node_id, zone_idx(zone), zone_start_pfn);
@@ -2844,8 +2843,8 @@ struct page *pfn_to_page(unsigned long p
  }
  unsigned long page_to_pfn(struct page *page)
  {
-	struct zone *zone = page_zone(page);
-	return (page - zone->zone_mem_map) + zone->zone_start_pfn;
+	struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
+	return (page - pgdat->node_mem_map) + pgdat->node_start_pfn;

  }
  #elif defined(CONFIG_SPARSEMEM)
Index: test/include/asm-alpha/mmzone.h
===================================================================
--- test.orig/include/asm-alpha/mmzone.h
+++ test/include/asm-alpha/mmzone.h
@@ -83,8 +83,7 @@ PLAT_NODE_DATA_LOCALNR(unsigned long p,
  	pte_t pte;                                                           \
  	unsigned long pfn;                                                   \
  									     \
-	pfn = ((unsigned long)((page)-page_zone(page)->zone_mem_map)) << 32; \
-	pfn += page_zone(page)->zone_start_pfn << 32;			     \
+	pfn = page_to_pfn(page) << 32; \
  	pte_val(pte) = pfn | pgprot_val(pgprot);			     \
  									     \
  	pte;								     \

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Re: [PATCH] remove zone_mem_map

[Andrew Morton]

KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>
> This patch removes zone_mem_map from zone.
>  By this, (generic) page_to_pfn and pfn_to_page can use the same logic.

I assume this is dependent upon unify-pfn_to_page-*.patch?

>  This modifies page_to_pfn implementation. Could anyone do performance test on NUMA ?

Do you expect there to be NUMA performance problems?  If so, how do they
arise and what sort of tests should be run?

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Re: [PATCH] remove zone_mem_map

[KAMEZAWA Hiroyuki]

Andrew Morton wrote:
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>> This patch removes zone_mem_map from zone.
>>  By this, (generic) page_to_pfn and pfn_to_page can use the same logic.
> 
> I assume this is dependent upon unify-pfn_to_page-*.patch?
> 
yes. sorry for forgetting to write it.

>>  This modifies page_to_pfn implementation. Could anyone do performance test on NUMA ?
> 
> Do you expect there to be NUMA performance problems?  If so, how do they
> arise and what sort of tests should be run?
> 
I don't expect it. But when I posted this before (as RFC), some persons
(Martin J. Bligh and Dave Hansen) had concerns about it.

I think the heaviest users of page_to_pfn() are the page allocator and
mk_pte(page_to_pfn(page), hogehoge).

So, tests like  "mmap -> touch all -> unmap" will be good test.

powerpc and ia64 is not a good test environment, because they don't use
page_to_pfn() of generic DISCONTIG definitions.

other NUMAs (i386, x86_64 etc..) will be good.

Thanks,
-- Kame

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Re: [PATCH] remove zone_mem_map

[Christoph Lameter]

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...

> 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.

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Re: [PATCH] remove zone_mem_map

[KAMEZAWA Hiroyuki]

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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Re: [PATCH] remove zone_mem_map

[Christoph Lameter]

On Wed, 22 Feb 2006, KAMEZAWA Hiroyuki wrote:

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

Well yes, we actually have virtual mappings in kernel address space. 
F.e. The hotplug remove issues could be fixed there by remapping pages.

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Re: [PATCH] remove zone_mem_map

[KAMEZAWA Hiroyuki]

Christoph Lameter wrote:
> On Wed, 22 Feb 2006, KAMEZAWA Hiroyuki wrote:
> 
>> BTW, ia64 looks very special. Does it make sensible performance gain ?
> 
> Well yes, we actually have virtual mappings in kernel address space. 
> F.e. The hotplug remove issues could be fixed there by remapping pages.
> 
Ah, if we place node_data[i](array of pointer to pgdat) in region 7,
there is no trouble ?
(maybe zone_table[] should be also..)

-- Kame

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