Re: [linux-next-20190214] Free pages statistics is broken.

[Vlastimil Babka <vbabka@suse.cz>]

On 2/15/19 3:27 PM, Tetsuo Handa wrote:
> On 2019/02/15 22:01, Michal Hocko wrote:
>> On Fri 15-02-19 11:27:10, Tetsuo Handa wrote:
>>> I noticed that amount of free memory reported by DMA: / DMA32: / Normal: fields are
>>> increasing over time. Since 5.0-rc6 is working correctly, some change in linux-next
>>> is causing this problem.
>> 
>> Just a shot into the dark. Could you try to disable the page allocator
>> randomization (page_alloc.shuffle kernel command line parameter)? Not
>> that I see any bug there but it is a recent change in the page allocator
>> I am aware of and it might have some anticipated side effects.
>> 
> 
> I tried CONFIG_SHUFFLE_PAGE_ALLOCATOR=n but problem still exists.

I think it's the preparation patch [1], even with randomization off:

@@ -1910,7 +1900,7 @@ static inline void expand(struct zone *zone, struct page *page,
                if (set_page_guard(zone, &page[size], high, migratetype))
                        continue;
 
-               list_add(&page[size].lru, &area->free_list[migratetype]);
+               add_to_free_area(&page[size], area, migratetype);
                area->nr_free++;
                set_page_order(&page[size], high);
        }

This should have removed the 'area->nr_free++;' line, as add_to_free_area()
includes the increment.

[1] https://www.ozlabs.org/~akpm/mmotm/broken-out/mm-move-buddy-list-manipulations-into-helpers.patch