Re: [PATCH] mm: memcontrol: Let mem_cgroup_move_account() have effect only if MMU enabled

[Johannes Weiner]

On Tue, Mar 03, 2015 at 02:45:24PM +0100, Michal Hocko wrote:
> On Tue 03-03-15 06:42:01, Chen Gang wrote:
> > When !MMU, it will report warning. The related warning with allmodconfig
> > under c6x:
> 
> Does it even make any sense to enable CONFIG_MEMCG when !CONFIG_MMU?
> Is anybody using this configuration and is it actually usable? My
> knowledge about CONFIG_MMU is close to zero so I might be missing
> something but I do not see a point into fixing compile warnings when
> the whole subsystem is not usable in the first place.

It's very limited, and anonymous memory is not even charged right now,
even though it could be -- see nommu.c::do_mmap_private().  But there
is nothing inherent in the memcg functionality that would require an
MMU I guess, except for these ridiculous charge moving pte walkers.

> > Signed-off-by: Chen Gang <gang.chen.5i5j@xxxxxxxxx>

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
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