linux-kernel - Re: [PATCH 17/25] Do not call get_pageblock

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Date:	Tue, 21 Apr 2009 20:03:10 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	kosaki.motohiro@...fujitsu.com,
	Linux Memory Management List <linux-mm@...ck.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 17/25] Do not call get_pageblock_migratetype() more than necessary

> get_pageblock_migratetype() is potentially called twice for every page
> free. Once, when being freed to the pcp lists and once when being freed
> back to buddy. When freeing from the pcp lists, it is known what the
> pageblock type was at the time of free so use it rather than rechecking.
> In low memory situations under memory pressure, this might skew
> anti-fragmentation slightly but the interference is minimal and
> decisions that are fragmenting memory are being made anyway.
> 
> Signed-off-by: Mel Gorman <mel@....ul.ie>
> Reviewed-by: Christoph Lameter <cl@...ux-foundation.org>
> ---
>  mm/page_alloc.c |   16 ++++++++++------
>  1 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index c57c602..a1ca038 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -456,16 +456,18 @@ static inline int page_is_buddy(struct page *page, struct page *buddy,
>   */
>  
>  static inline void __free_one_page(struct page *page,
> -		struct zone *zone, unsigned int order)
> +		struct zone *zone, unsigned int order,
> +		int migratetype)
>  {
>  	unsigned long page_idx;
>  	int order_size = 1 << order;
> -	int migratetype = get_pageblock_migratetype(page);
>  
>  	if (unlikely(PageCompound(page)))
>  		if (unlikely(destroy_compound_page(page, order)))
>  			return;
>  
> +	VM_BUG_ON(migratetype == -1);
> +
>  	page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
>  
>  	VM_BUG_ON(page_idx & (order_size - 1));
> @@ -534,17 +536,18 @@ static void free_pages_bulk(struct zone *zone, int count,
>  		page = list_entry(list->prev, struct page, lru);
>  		/* have to delete it as __free_one_page list manipulates */
>  		list_del(&page->lru);
> -		__free_one_page(page, zone, order);
> +		__free_one_page(page, zone, order, page_private(page));
>  	}
>  	spin_unlock(&zone->lock);

looks good.
	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>


btw, I can't review rest patch today. I plan to do that tommorow, sorry.



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