Re: [RFC PATCH] mm, page_alloc: avoid page_to_pfn() in move_freepages()

[David Hildenbrand <david@redhat.com>]

[...]

>  static int move_freepages(struct zone *zone,
> -			  struct page *start_page, struct page *end_page,
> +			  unsigned long start_pfn, unsigned long end_pfn,
>  			  int migratetype, int *num_movable)
>  {
>  	struct page *page;
> +	unsigned long pfn;
>  	unsigned int order;
>  	int pages_moved = 0;
>  
> -	for (page = start_page; page <= end_page;) {
> -		if (!pfn_valid_within(page_to_pfn(page))) {
> -			page++;
> +	for (pfn = start_pfn; pfn <= end_pfn;) {
> +		if (!pfn_valid_within(pfn)) {
> +			pfn++;
>  			continue;
>  		}
>  
> +		page = pfn_to_page(pfn);
>  		if (!PageBuddy(page)) {
>  			/*
>  			 * We assume that pages that could be isolated for
> @@ -2268,8 +2270,7 @@ static int move_freepages(struct zone *zone,
>  			if (num_movable &&
>  					(PageLRU(page) || __PageMovable(page)))
>  				(*num_movable)++;
> -
> -			page++;
> +			pfn++;
>  			continue;
>  		}
>  
> @@ -2280,6 +2281,7 @@ static int move_freepages(struct zone *zone,
>  		order = page_order(page);
>  		move_to_free_area(page, &zone->free_area[order], migratetype);
>  		page += 1 << order;

You can drop this now as well, no?

> +		pfn += 1 << order;
>  		pages_moved += 1 << order;
>  	}
>  
> @@ -2289,25 +2291,22 @@ static int move_freepages(struct zone *zone,
>  int move_freepages_block(struct zone *zone, struct page *page,
>  				int migratetype, int *num_movable)
>  {
> -	unsigned long start_pfn, end_pfn;
> -	struct page *start_page, *end_page;
> +	unsigned long start_pfn, end_pfn, pfn;
>  
>  	if (num_movable)
>  		*num_movable = 0;
>  
> -	start_pfn = page_to_pfn(page);
> +	pfn = start_pfn = page_to_pfn(page);

pfn = page_to_pfn(page);

and ...

>  	start_pfn = start_pfn & ~(pageblock_nr_pages-1);

...

start_pfn = pfn & ~(pageblock_nr_pages - 1);

instead?

> -	start_page = pfn_to_page(start_pfn);
> -	end_page = start_page + pageblock_nr_pages - 1;
>  	end_pfn = start_pfn + pageblock_nr_pages - 1;
>  
>  	/* Do not cross zone boundaries */
>  	if (!zone_spans_pfn(zone, start_pfn))
> -		start_page = page;
> +		start_pfn = pfn;
>  	if (!zone_spans_pfn(zone, end_pfn))
>  		return 0;
>  
> -	return move_freepages(zone, start_page, end_page, migratetype,
> +	return move_freepages(zone, start_pfn, end_pfn, migratetype,
>  								num_movable);
>  }
>  
> 


-- 
Thanks,

David / dhildenb