[PATCH] mm: fix set pageblock migratetype when boot

[PATCH] mm: fix set pageblock migratetype when boot

[Xishi Qiu]

memmap_init_zone()
	...
	if ((z->zone_start_pfn <= pfn)
	    && (pfn < zone_end_pfn(z))
	    && !(pfn & (pageblock_nr_pages - 1)))
		set_pageblock_migratetype(page, MIGRATE_MOVABLE);
	...

If the pfn does not align to pageblock, it will not init the migratetype.
So call it for every page, it will takes more time, but it doesn't matter, 
this function will be called only in boot or hotadd memory.

e.g.
[  223.679446]   node   0: [mem 0x00001000-0x00099fff]
[  223.679449]   node   0: [mem 0x00100000-0xbf78ffff]
[  223.680486]   node   0: [mem 0x100000000-0x27fffffff]

Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
---
 mm/page_alloc.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ebffa0e..a1df227 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4210,8 +4210,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 		 * pfn out of zone.
 		 */
 		if ((z->zone_start_pfn <= pfn)
-		    && (pfn < zone_end_pfn(z))
-		    && !(pfn & (pageblock_nr_pages - 1)))
+		    && (pfn < zone_end_pfn(z)))
 			set_pageblock_migratetype(page, MIGRATE_MOVABLE);
 
 		INIT_LIST_HEAD(&page->lru);
-- 
1.7.1

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Re: [PATCH] mm: fix set pageblock migratetype when boot

[Mel Gorman]

On Fri, Jun 26, 2015 at 06:09:05PM +0800, Xishi Qiu wrote:
> memmap_init_zone()
> 	...
> 	if ((z->zone_start_pfn <= pfn)
> 	    && (pfn < zone_end_pfn(z))
> 	    && !(pfn & (pageblock_nr_pages - 1)))
> 		set_pageblock_migratetype(page, MIGRATE_MOVABLE);
> 	...
> 
> If the pfn does not align to pageblock, it will not init the migratetype.

What important impact does that have? It should leave a partial pageblock
as MIGRATE_UNMOVABLE which is fine by me.

> So call it for every page, it will takes more time, but it doesn't matter, 
> this function will be called only in boot or hotadd memory.
> 

It's a lot of additional overhead to add to memory initialisation. It
would need to be for an excellent reason with no alternative solution.

-- 
Mel Gorman
SUSE Labs

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Re: [PATCH] mm: fix set pageblock migratetype when boot

[Xishi Qiu]

On 2015/6/26 19:04, Mel Gorman wrote:

> On Fri, Jun 26, 2015 at 06:09:05PM +0800, Xishi Qiu wrote:
>> memmap_init_zone()
>> 	...
>> 	if ((z->zone_start_pfn <= pfn)
>> 	    && (pfn < zone_end_pfn(z))
>> 	    && !(pfn & (pageblock_nr_pages - 1)))
>> 		set_pageblock_migratetype(page, MIGRATE_MOVABLE);
>> 	...
>>
>> If the pfn does not align to pageblock, it will not init the migratetype.
> 
> What important impact does that have? It should leave a partial pageblock
> as MIGRATE_UNMOVABLE which is fine by me.
> 

Hi Mel,

The impact is less, it's OK to ignore it.

Thanks,
Xishi Qiu

>> So call it for every page, it will takes more time, but it doesn't matter, 
>> this function will be called only in boot or hotadd memory.
>>
> 
> It's a lot of additional overhead to add to memory initialisation. It
> would need to be for an excellent reason with no alternative solution.
> 



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