Re: [patch] mm: memcontrol: lockless page counters

[Michal Hocko]

On Mon 22-09-14 11:50:49, Johannes Weiner wrote:
> On Mon, Sep 22, 2014 at 04:44:36PM +0200, Michal Hocko wrote:
> > On Fri 19-09-14 09:22:08, Johannes Weiner wrote:
[...]
> > Nevertheless I think that the counter should live outside of memcg (it
> > is ugly and bad in general to make HUGETLB controller depend on MEMCG
> > just to have a counter). If you made kernel/page_counter.c and led both
> > containers select CONFIG_PAGE_COUNTER then you do not need a dependency
> > on MEMCG and I would find it cleaner in general.
> 
> The reason I did it this way is because the hugetlb controller simply
> accounts and limits a certain type of memory and in the future I would
> like to make it a memcg extension, just like kmem and swap.

I am not sure this is the right way to go. Hugetlb has always been
"special" and I do not see any advantage to pull its specialness into
memcg proper. It would just make the code more complicated. I can also
imagine users who simply do not want to pay memcg overhead and use only
hugetlb controller.

Besides that it is not like a separate page_counter with a clear
interface would cause more maintenance overhead so I really do not see
any reason to pull it into memcg.
-- 
Michal Hocko
SUSE Labs
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