linux-kernel - Re: [RFC PATCH v3 09/35] mm: Track the freepage migratetype of pages accurately

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Message-ID: <522583DE.709@jp.fujitsu.com>
Date:	Tue, 3 Sep 2013 15:38:22 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
CC:	<akpm@...ux-foundation.org>, <mgorman@...e.de>,
	<hannes@...xchg.org>, <tony.luck@...el.com>,
	<matthew.garrett@...ula.com>, <dave@...1.net>, <riel@...hat.com>,
	<arjan@...ux.intel.com>, <srinivas.pandruvada@...ux.intel.com>,
	<willy@...ux.intel.com>, <kamezawa.hiroyu@...fujitsu.com>,
	<lenb@...nel.org>, <rjw@...k.pl>, <gargankita@...il.com>,
	<paulmck@...ux.vnet.ibm.com>, <svaidy@...ux.vnet.ibm.com>,
	<andi@...stfloor.org>, <santosh.shilimkar@...com>,
	<kosaki.motohiro@...il.com>, <linux-pm@...r.kernel.org>,
	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v3 09/35] mm: Track the freepage migratetype of pages
 accurately

(2013/08/30 22:16), Srivatsa S. Bhat wrote:
> Due to the region-wise ordering of the pages in the buddy allocator's
> free lists, whenever we want to delete a free pageblock from a free list
> (for ex: when moving blocks of pages from one list to the other), we need
> to be able to tell the buddy allocator exactly which migratetype it belongs
> to. For that purpose, we can use the page's freepage migratetype (which is
> maintained in the page's ->index field).
>
> So, while splitting up higher order pages into smaller ones as part of buddy
> operations, keep the new head pages updated with the correct freepage
> migratetype information (because we depend on tracking this info accurately,
> as outlined above).
>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> ---
>
>   mm/page_alloc.c |    7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 398b62c..b4b1275 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -947,6 +947,13 @@ static inline void expand(struct zone *zone, struct page *page,
>   		add_to_freelist(&page[size], &area->free_list[migratetype]);
>   		area->nr_free++;
>   		set_page_order(&page[size], high);
> +
> +		/*
> +		 * Freepage migratetype is tracked using the index field of the
> +		 * first page of the block. So we need to update the new first
> +		 * page, when changing the page order.
> +		 */
> +		set_freepage_migratetype(&page[size], migratetype);
>   	}
>   }
>
>

It this patch a bug fix patch?
If so, I want you to split the patch from the patch-set.

Thanks,
Yasuaki Ishimatsu


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