Re: [PATCH 2/3] mm: page allocator: Calculate a better estimate ofNR_FREE_PAGES when memory is low and kswapd is awake

[Christoph Lameter]

On Tue, 31 Aug 2010, Mel Gorman wrote:

> +#ifdef CONFIG_SMP
> +/* Called when a more accurate view of NR_FREE_PAGES is needed */
> +unsigned long zone_nr_free_pages(struct zone *zone)
> +{
> +	unsigned long nr_free_pages = zone_page_state(zone, NR_FREE_PAGES);

You cannot call zone_page_state here because zone_page_state clips the
counter at zero. The nr_free_pages needs to reflect the unclipped state
and then the deltas need to be added. Then the clipping at zero can be
done.
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