Re: [PATCH 2/2] mm, slab: Extend vm/drop_caches to shrink kmem slabs

[Roman Gushchin]

On Fri, Jun 28, 2019 at 03:32:28PM +0000, Christopher Lameter wrote:
> On Thu, 27 Jun 2019, Roman Gushchin wrote:
> 
> > so that objects belonging to different memory cgroups can share the same page
> > and kmem_caches.
> >
> > It's a fairly big change though.
> 
> Could this be done at another level? Put a cgoup pointer into the
> corresponding structures and then go back to just a single kmen_cache for
> the system as a whole?
> You can still account them per cgroup and there
> will be no cleanup problem anymore. You could scan through a slab cache
> to remove the objects of a certain cgroup and then the fragmentation
> problem that cgroups create here will be handled by the slab allocators in
> the traditional way. The duplication of the kmem_cache was not designed
> into the allocators but bolted on later.
> 

Yeah, this is exactly what I'm talking about. Idk how big the performance
penalty will be for small and short-living objects, it should be measured.
But for long-living objects it will be much better for sure...

Thanks!