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Message-ID: <20190628163334.GA3118@tower.DHCP.thefacebook.com>
Date: Fri, 28 Jun 2019 16:33:41 +0000
From: Roman Gushchin <guro@...com>
To: Christopher Lameter <cl@...ux.com>
CC: Waiman Long <longman@...hat.com>,
Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Jonathan Corbet <corbet@....net>,
Luis Chamberlain <mcgrof@...nel.org>,
Kees Cook <keescook@...omium.org>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>,
Vladimir Davydov <vdavydov.dev@...il.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Shakeel Butt <shakeelb@...gle.com>,
Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH 2/2] mm, slab: Extend vm/drop_caches to shrink kmem slabs
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!
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