Re: [PATCH] mm: use managed_zone() for more exact check in zone iteration

[osalvador]

On Fri, 2018-11-16 at 10:57 +0100, Michal Hocko wrote:
> On Thu 15-11-18 13:37:35, Andrew Morton wrote:
> [...]
> > Worse, the situations in which managed_zone() != populated_zone()
> > are
> > rare(?), so it will take a long time for problems to be discovered,
> > I
> > expect.
> 
> We would basically have to deplete the whole zone by the bootmem
> allocator or pull out all pages from the page allocator. E.g. memory
> hotplug decreases both managed and present counters. I am actually
> not
> sure that is 100% correct (put on my TODO list to check). There is no
> consistency in that regards.

We can only offline non-reserved pages (so, managed pages).
Since present pages holds reserved_pages + managed_pages, decreasing
both should be fine unless I am mistaken.

Oscar Salvador