Re: [PATCH v2 04/29] slub: always get the cache from its page inkfree

[Glauber Costa]

On 05/11/2012 04:09 PM, Christoph Lameter wrote:
> On Fri, 11 May 2012, Glauber Costa wrote:
>
> > On 05/11/2012 03:56 PM, Christoph Lameter wrote:
> > > On Fri, 11 May 2012, Glauber Costa wrote:
> > >
> > > > So we don't mix pages from multiple memcgs in the same cache - we believe
> > > > that
> > > > would be too confusing.
> > >
> > > Well subsystem create caches and other things that are shared between
> > > multiple processes. How can you track that?
> >
> > Each process that belongs to a memcg triggers the creation of a new child kmem
> > cache.
>
> I see that. But there are other subsystems from slab allocators that do
> the same. There are also objects that may be used by multiple processes.

This is also true for normal user pages. And then, we do what memcg 
does: first one to touch, gets accounted. I don't think deviating from 
the memcg behavior for user pages makes much sense here.

A cache won't go away while it still have objects, even after the memcg 
is removed (it is marked as dead)

> F.e what about shm?
>
> > > > /proc/slabinfo reflects this information, by listing the memcg-specific
> > > > slabs.
> > >
> > > What about /sys/kernel/slab/*?
> >
> >  From the PoV of the global system, what you'll see is something like:
> > dentry , dentry(2:memcg1), dentry(2:memcg2), etc.
>
> Hmmm.. Would be better to have a hierachy there. /proc/slabinfo is more
> legacy.

I can take a look at that then. Assuming you agree with all the rest, is 
looking into that a pre-requisite for merging, or is something that can 
be deferred for a phase2 ? (We still don't do shrinkers, for instance, 
so this is sure to have a phase2)
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