[Devel] Re: [PATCH v2 04/11] kmem accounting basic infrastructure

[Christoph Lameter]

On Wed, 15 Aug 2012, Glauber Costa wrote:

> On 08/15/2012 06:47 PM, Christoph Lameter wrote:
> > On Wed, 15 Aug 2012, Michal Hocko wrote:
> >
> >>> That is not what the kernel does, in general. We assume that if he wants
> >>> that memory and we can serve it, we should. Also, not all kernel memory
> >>> is unreclaimable. We can shrink the slabs, for instance. Ying Han
> >>> claims she has patches for that already...
> >>
> >> Are those patches somewhere around?
> >
> > You can already shrink the reclaimable slabs (dentries / inodes) via
> > calls to the subsystem specific shrinkers. Did Ying Han do anything to
> > go beyond that?
> >
> That is not enough for us.
> We would like to make sure that the objects being discarded belong to
> the memcg which is under pressure. We don't need to be perfect here, and
> an occasional slip is totally fine. But if in general, shrinking from
> memcg A will mostly wipe out objects from memcg B, we harmed the system
> in return for nothing good.

How can you figure out which objects belong to which memcg? The ownerships
of dentries and inodes is a dubious concept already.