Re: [PATCH 4.2 25/54] memcg: convert threshold to bytes

Michal Hocko
2015-10-27T10:31:49Z

On Sun 25-10-15 17:32:10, Michal Hocko wrote:
> On Sat 24-10-15 14:46:58, Ben Hutchings wrote:
> [...]
> > > --- a/mm/memcontrol.c
> > > +++ b/mm/memcontrol.c
> > > @@ -3687,6 +3687,7 @@ static int __mem_cgroup_usage_register_e
> > >  > > ret = page_counter_memparse(args, "-1", &threshold);
> > >  > > if (ret)
> > >  > > > return ret;
> > > +> > threshold <<= PAGE_SHIFT;
> > >
> > >  > > mutex_lock(&memcg->thresholds_lock);
> > >
> >
> > mem_cgroup_usage() returns a u64 and I think that the types of
> > threshold and mem_cgroup_threshold::threshold also need be changed to
> > u64 to avoid overflow on large 32-bit systems.
>
> You are absolutely right! I have compltely missed that 3e32cb2e0a12 has
> changed the type as well. Should have noticed that during the review.
>
> The whole thing is just way too confusing. All the tracking is done in
> page units yet tresholds are in bytes. This only calls for troubles. The
> patch below simply turns thresholds to page units as well. I hope I
> haven't screwed anything, I didn't get to more than compile test it.

OK, I've tested it and it seems working as expected. I will repost to
the linux-mm mailing list.
--
Michal Hocko
SUSE Labs