linux-kernel - Re: [PATCH v2 2/3] mm: remain migratetype in freed page

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Date:	Thu, 06 Sep 2012 15:13:08 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Minchan Kim <minchan@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Xishi Qiu <qiuxishi@...wei.com>,
	Wen Congyang <wency@...fujitsu.com>
Subject: Re: [PATCH v2 2/3] mm: remain migratetype in freed page

(2012/09/06 14:16), Minchan Kim wrote:
> The page allocator caches the pageblock information in page->private while
> it is in the PCP freelists but this is overwritten with the order of the
> page when freed to the buddy allocator. This patch stores the migratetype
> of the page in the page->index field so that it is available at all times
> when the page remain in free_list.
> 
sounds reasonable.

> This patch adds a new call site in __free_pages_ok so it might be
> overhead a bit but it's for high order allocation.
> So I believe damage isn't hurt.
> 
> * from v1
>    * Fix move_freepages's migratetype - Mel
>    * Add more kind explanation in description - Mel
> 
> Signed-off-by: Minchan Kim <minchan@...nel.org>

Hmm, page->index is valid only when the page is the head of buddy chunk ?

Anyway,

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

> ---
>   include/linux/mm.h |    4 ++--
>   mm/page_alloc.c    |    7 +++++--
>   2 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 84d1663f..68f9e8d 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -240,13 +240,13 @@ struct inode;
>   /* It's valid only if the page is free path or free_list */
>   static inline void set_freepage_migratetype(struct page *page, int migratetype)
>   {
> -	set_page_private(page, migratetype);
> +	page->index = migratetype;
>   }
>   
>   /* It's valid only if the page is free path or free_list */
>   static inline int get_freepage_migratetype(struct page *page)
>   {
> -	return page_private(page);
> +	return page->index;
>   }
>   
>   /*
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index f5ba236..8531fa3 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -723,6 +723,7 @@ static void __free_pages_ok(struct page *page, unsigned int order)
>   {
>   	unsigned long flags;
>   	int wasMlocked = __TestClearPageMlocked(page);
> +	int migratetype;
>   
>   	if (!free_pages_prepare(page, order))
>   		return;
> @@ -731,8 +732,9 @@ static void __free_pages_ok(struct page *page, unsigned int order)
>   	if (unlikely(wasMlocked))
>   		free_page_mlock(page);
>   	__count_vm_events(PGFREE, 1 << order);
> -	free_one_page(page_zone(page), page, order,
> -					get_pageblock_migratetype(page));
> +	migratetype = get_pageblock_migratetype(page);
> +	set_freepage_migratetype(page, migratetype);
> +	free_one_page(page_zone(page), page, order, migratetype);
>   	local_irq_restore(flags);
>   }
>   
> @@ -952,6 +954,7 @@ static int move_freepages(struct zone *zone,
>   		order = page_order(page);
>   		list_move(&page->lru,
>   			  &zone->free_area[order].free_list[migratetype]);
> +		set_freepage_migratetype(page, migratetype);
>   		page += 1 << order;
>   		pages_moved += 1 << order;
>   	}
> 


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