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

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2019/11/27 18:47, David Hildenbrand wrote:
> [...]
> 
>>  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?

should do it

> 
>> +		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?

will change， thanks for your comments.

> 
>> -	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);
>>  }
>>  
>>
> 
>