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From:   Roman Gushchin <guro@fb.com>
To:     Christopher Lameter <cl@linux.com>
CC:     Waiman Long <longman@redhat.com>,
        Pekka Enberg <penberg@kernel.org>,
        "David Rientjes" <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
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        Michal Hocko <mhocko@kernel.org>,
        "Johannes Weiner" <hannes@cmpxchg.org>,
        Shakeel Butt <shakeelb@google.com>,
        "Vladimir Davydov" <vdavydov.dev@gmail.com>
Subject: Re: [PATCH v2 1/2] mm, slab: Extend slab/shrink to shrink all memcg
 caches
Thread-Topic: [PATCH v2 1/2] mm, slab: Extend slab/shrink to shrink all memcg
 caches
Thread-Index: AQHVPN3TlomcCJJgFEONei6lr3vfPKbQQNKAgABbTQA=
Date:   Thu, 18 Jul 2019 17:05:04 +0000
Message-ID: <20190718170458.GA6139@castle.dhcp.thefacebook.com>
References: <20190717202413.13237-1-longman@redhat.com>
 <20190717202413.13237-2-longman@redhat.com>
 <0100016c04e0192f-299df02d-a35f-46db-9833-37ba7a01f5f0-000000@email.amazonses.com>
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On Thu, Jul 18, 2019 at 11:38:11AM +0000, Christopher Lameter wrote:
> On Wed, 17 Jul 2019, Waiman Long wrote:
>=20
> > Currently, a value of '1" is written to /sys/kernel/slab/<slab>/shrink
> > file to shrink the slab by flushing out all the per-cpu slabs and free
> > slabs in partial lists. This can be useful to squeeze out a bit more me=
mory
> > under extreme condition as well as making the active object counts in
> > /proc/slabinfo more accurate.
>=20
> Acked-by: Christoph Lameter <cl@linux.com>
>=20
> >  # grep task_struct /proc/slabinfo
> >  task_struct        53137  53192   4288   61    4 : tunables    0    0
> >  0 : slabdata    872    872      0
> >  # grep "^S[lRU]" /proc/meminfo
> >  Slab:            3936832 kB
> >  SReclaimable:     399104 kB
> >  SUnreclaim:      3537728 kB
> >
> > After shrinking slabs:
> >
> >  # grep "^S[lRU]" /proc/meminfo
> >  Slab:            1356288 kB
> >  SReclaimable:     263296 kB
> >  SUnreclaim:      1092992 kB
>=20
> Well another indicator that it may not be a good decision to replicate th=
e
> whole set of slabs for each memcg. Migrate the memcg ownership into the
> objects may allow the use of the same slab cache. In particular together
> with the slab migration patches this may be a viable way to reduce memory
> consumption.
>=20

Btw I'm working on an alternative solution. It's way too early to present
anything, but preliminary results are looking promising: slab memory usage
is decreased by 10-40% depending on the workload.

Thanks!