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

[Dan Williams <dan.j.williams@intel.com>]

On Fri, Feb 15, 2019 at 9:44 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> 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.

Yes, good find! I'll send an incremental fixup patch in a moment
unless someone beats me to it.