Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using page->lru field

[Jerome Glisse]

On Mon, Jul 10, 2017 at 07:48:58PM +0200, Michal Hocko wrote:
> On Mon 10-07-17 12:54:21, Jerome Glisse wrote:
> > On Mon, Jul 10, 2017 at 06:36:52PM +0200, Michal Hocko wrote:
> > > On Mon 10-07-17 12:25:42, Jerome Glisse wrote:
> > > [...]
> > > > Bottom line is that we can always free and uncharge device memory
> > > > page just like any regular page.
> > > 
> > > OK, this answers my earlier question. Then it should be feasible to
> > > charge this memory. There are still some things to handle. E.g. how do
> > > we consider this memory during oom victim selection (this is not
> > > accounted as an anonymous memory in get_mm_counter, right?), maybe others.
> > > But the primary point is that nobody pins the memory outside of the
> > > mapping.
> > 
> > At this point it is accounted as a regular page would be (anonymous, file
> > or share memory). I wanted mm_counters to reflect memcg but i can untie
> > that.
> 
> I am not sure I understand. If the device memory is accounted to the
> same mm counter as the original page then it is correct. I will try to
> double check the implementation (hopefully soon).

It is accounted like the original page. By same as memcg i mean i made
the same kind of choice for mm counter than i made for memcg. It is
all in the migrate code (migrate.c) ie i don't touch any of the mm
counter when migrating page.

Jérôme