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From:   Roman Gushchin <guro@fb.com>
To:     Christopher Lameter <cl@linux.com>
CC:     Waiman Long <longman@redhat.com>,
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Subject: Re: [PATCH 2/2] mm, slab: Extend vm/drop_caches to shrink kmem slabs
Thread-Topic: [PATCH 2/2] mm, slab: Extend vm/drop_caches to shrink kmem slabs
Thread-Index: AQHVKrRnjGLXeWaE8kq5EhXDbrxOt6auY3OAgAGdGgCAAAdmgIABMAYAgAAREwA=
Date:   Fri, 28 Jun 2019 16:33:41 +0000
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On Fri, Jun 28, 2019 at 03:32:28PM +0000, Christopher Lameter wrote:
> On Thu, 27 Jun 2019, Roman Gushchin wrote:
>=20
> > so that objects belonging to different memory cgroups can share the sam=
e page
> > and kmem_caches.
> >
> > It's a fairly big change though.
>=20
> 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 i=
n
> the traditional way. The duplication of the kmem_cache was not designed
> into the allocators but bolted on later.
>=20

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!