Re: [PATCH RFC 3/4] mm/page_alloc: always move pages to the tail of the freelist in unset_migratetype_isolate()

[Vlastimil Babka <vbabka@xxxxxxx>]

On 9/25/20 10:05 AM, David Hildenbrand wrote:
>>>>  static inline void del_page_from_free_list(struct page *page, struct zone 
>>>> *zone,
>>>>                                       unsigned int order)
>>>>  {
>>>> @@ -2323,7 +2332,7 @@ static inline struct page 
>>>> *__rmqueue_cma_fallback(struct zone *zone,
>>>>   */
>>>>  static int move_freepages(struct zone *zone,
>>>>                      struct page *start_page, struct page *end_page,
>>>> -                    int migratetype, int *num_movable)
>>>> +                    int migratetype, int *num_movable, bool to_tail)
>>>>  {
>>>>    struct page *page;
>>>>    unsigned int order;
>>>> @@ -2354,7 +2363,10 @@ static int move_freepages(struct zone *zone,
>>>>            VM_BUG_ON_PAGE(page_zone(page) != zone, page);
>>>>  
>>>>            order = page_order(page);
>>>> -          move_to_free_list(page, zone, order, migratetype);
>>>> +          if (to_tail)
>>>> +                  move_to_free_list_tail(page, zone, order, migratetype);
>>>> +          else
>>>> +                  move_to_free_list(page, zone, order, migratetype);
>>>>            page += 1 << order;
>>>>            pages_moved += 1 << order;
>>>>    }
>>>> @@ -2362,8 +2374,9 @@ static int move_freepages(struct zone *zone,
>>>>    return pages_moved;
>>>>  }
>>>>  
>>>> -int move_freepages_block(struct zone *zone, struct page *page,
>>>> -                          int migratetype, int *num_movable)
>>>> +static int __move_freepages_block(struct zone *zone, struct page *page,
>>>> +                            int migratetype, int *num_movable,
>>>> +                            bool to_tail)
>>>>  {
>>>>    unsigned long start_pfn, end_pfn;
>>>>    struct page *start_page, *end_page;
>>>> @@ -2384,7 +2397,20 @@ int move_freepages_block(struct zone *zone, struct 
>>>> page *page,
>>>>            return 0;
>>>>  
>>>>    return move_freepages(zone, start_page, end_page, migratetype,
>>>> -                                                          num_movable);
>>>> +                        num_movable, to_tail);
>>>> +}
>>>> +
>>>> +int move_freepages_block(struct zone *zone, struct page *page,
>>>> +                   int migratetype, int *num_movable)
>>>> +{
>>>> +  return __move_freepages_block(zone, page, migratetype, num_movable,
>>>> +                                false);
>>>> +}
>>>> +
>>>> +int move_freepages_block_tail(struct zone *zone, struct page *page,
>>>> +                        int migratetype)
>>>> +{
>>>> +  return __move_freepages_block(zone, page, migratetype, NULL, true);
>>>>  }
>>>
>>> Likewise, just 5 callers of move_freepages_block(), all in the files you're
>>> already changing, so no need for this wrappers IMHO.
> 
> As long as we don't want to move the implementation to the header, we'll
> need it for the constant propagation to work at compile time (we don't
> really have link-time optimizations). Or am I missing something?

I guess move_freepages_block() is not exactly fast path, so we could do without 
it.

> Thanks!
>