linux-kernel - Re: [PATCH 1/6] PM / Hibernate: Create a Radix-Tree to store memory bitmap

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Date:	Tue, 22 Jul 2014 00:36:37 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Pavel Machek <pavel@....cz>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH 1/6] PM / Hibernate: Create a Radix-Tree to store memory
 bitmap

Pavel,

On Mon, Jul 21, 2014 at 12:26:57PM +0200, Joerg Roedel wrote:
>  unsigned int snapshot_additional_pages(struct zone *zone)
>  {
> +	unsigned int rtree, nodes;
>  	unsigned int res;
>  
>  	res = DIV_ROUND_UP(zone->spanned_pages, BM_BITS_PER_BLOCK);
>  	res += DIV_ROUND_UP(res * sizeof(struct bm_block),
>  			    LINKED_PAGE_DATA_SIZE);
> -	return 2 * res;
> +	rtree = nodes = DIV_ROUND_UP(zone->spanned_pages, BM_BITS_PER_BLOCK);
> +	rtree += DIV_ROUND_UP(rtree * sizeof(struct rtree_node),
> +			      LINKED_PAGE_DATA_SIZE);
> +	while (nodes > 1) {
> +		nodes = DIV_ROUND_UP(nodes, BM_ENTRIES_PER_LEVEL);
> +		rtree += nodes;
> +	}
> +
> +	return 2 * (res + rtree);
>  }

Since you asked in another mail if I took the new data structure size
requirements into account, here is the code I added for this
computation.

Note that the above diff leaves the old code around because the old
memory bitmap implementation is not removed before patch 5/6 (which also
removes the old computation). So the final code will only have the new
size calculation in it.

Do you have any more concerns?


	Joerg

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