From: Andrew Morton <akpm@linux-foundation.org>
To: Christoph Lameter <cl@linux.com>
Cc: Glauber Costa <glommer@parallels.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kamezawa.hiroyu@jp.fujitsu.com,
Johannes Weiner <hannes@cmpxchg.org>, Tejun Heo <tj@kernel.org>,
Michal Hocko <mhocko@suse.cz>, Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Pekka Enberg <penberg@cs.helsinki.fi>,
Suleiman Souhlal <suleiman@google.com>
Subject: Re: [PATCH v6 25/29] memcg/sl[au]b: shrink dead caches
Date: Thu, 8 Nov 2012 11:21:20 -0800 [thread overview]
Message-ID: <20121108112120.fc964c29.akpm@linux-foundation.org> (raw)
In-Reply-To: <0000013ae1050e6f-7f908e0b-720a-4e68-a275-e5086a4f5c74-000000@email.amazonses.com>
On Thu, 8 Nov 2012 17:15:36 +0000
Christoph Lameter <cl@linux.com> wrote:
> On Wed, 7 Nov 2012, Andrew Morton wrote:
>
> > What's up with kmem_cache_shrink? It's global and exported to modules
> > but its only external caller is some weird and hopelessly poorly
> > documented site down in drivers/acpi/osl.c. slab and slob implement
> > kmem_cache_shrink() *only* for acpi! wtf? Let's work out what acpi is
> > trying to actually do there, then do it properly, then killkillkill!
>
> kmem_cache_shrink is also used internally. Its simply releasing unused
> cached objects.
Only in slub. It could be removed outright from the others and
simplified in slub.
> > Secondly, as slab and slub (at least) have the ability to shed cached
> > memory, why aren't they hooked into the core cache-shinking machinery.
> > After all, it's called "shrink_slab"!
>
> Because the core cache shrinking needs the slab caches to free up memory
> from inodes and dentries. We could call kmem_cache_shrink at the end of
> the shrink passes in vmscan. The price would be that the caches would have
> to be repopulated when new allocations occur.
Well, the shrinker shouldn't strips away all the cache. It will perform
a partial trim, the magnitude of which increases with perceived
external memory pressure.
AFACIT, this is correct and desirable behaviour for shrinking
slab's internal caches.
> >
> > If we can fix all that up then I wonder whether this particular patch
> > needs to exist at all. If the kmem_cache is no longer used then we
> > can simply leave it floating around in memory and the regular cache
> > shrinking code out of shrink_slab() will clean up any remaining pages.
> > The kmem_cache itself can be reclaimed via another shrinker, if
> > necessary?
>
> The kmem_cache can only be released if all its objects (used and unused)
> are released. kmem_cache_shrink drops the unused objects on some internal
> slab specific list. That may enable us to release the kmem_cache
> structure.
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next prev parent reply other threads:[~2012-11-08 19:21 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-01 12:07 [PATCH v6 00/29] kmem controller for memcg Glauber Costa
2012-11-01 12:07 ` [PATCH v6 01/29] memcg: Make it possible to use the stock for more than one page Glauber Costa
2012-11-01 12:07 ` [PATCH v6 02/29] memcg: Reclaim when more than one page needed Glauber Costa
2012-11-01 12:07 ` [PATCH v6 03/29] memcg: change defines to an enum Glauber Costa
2012-11-01 12:07 ` [PATCH v6 04/29] kmem accounting basic infrastructure Glauber Costa
2012-11-01 12:07 ` [PATCH v6 05/29] Add a __GFP_KMEMCG flag Glauber Costa
2012-11-01 19:58 ` Christoph Lameter
2012-11-01 12:07 ` [PATCH v6 06/29] memcg: kmem controller infrastructure Glauber Costa
2012-11-01 20:03 ` Christoph Lameter
2012-11-01 12:07 ` [PATCH v6 07/29] mm: Allocate kernel pages to the right memcg Glauber Costa
2012-11-01 12:07 ` [PATCH v6 08/29] res_counter: return amount of charges after res_counter_uncharge Glauber Costa
2012-11-01 12:07 ` [PATCH v6 09/29] memcg: kmem accounting lifecycle management Glauber Costa
2012-11-01 12:07 ` [PATCH v6 10/29] memcg: use static branches when code not in use Glauber Costa
2012-11-01 12:07 ` [PATCH v6 11/29] memcg: allow a memcg with kmem charges to be destructed Glauber Costa
2012-11-02 0:05 ` Andrew Morton
2012-11-02 7:50 ` Glauber Costa
2012-11-06 10:54 ` Michal Hocko
2012-11-01 12:07 ` [PATCH v6 12/29] execute the whole memcg freeing in free_worker Glauber Costa
2012-11-01 12:07 ` [PATCH v6 13/29] protect architectures where THREAD_SIZE >= PAGE_SIZE against fork bombs Glauber Costa
2012-11-01 12:07 ` [PATCH v6 14/29] Add documentation about the kmem controller Glauber Costa
2012-11-01 12:07 ` [PATCH v6 15/29] slab/slub: struct memcg_params Glauber Costa
2012-11-01 12:07 ` [PATCH v6 16/29] slab: annotate on-slab caches nodelist locks Glauber Costa
2012-11-01 12:07 ` [PATCH v6 17/29] consider a memcg parameter in kmem_create_cache Glauber Costa
2012-11-01 12:07 ` [PATCH v6 18/29] Allocate memory for memcg caches whenever a new memcg appears Glauber Costa
2012-11-06 0:23 ` Andrew Morton
2012-11-07 7:05 ` Glauber Costa
2012-11-07 7:10 ` Andrew Morton
2012-11-01 12:07 ` [PATCH v6 19/29] memcg: infrastructure to match an allocation to the right cache Glauber Costa
2012-11-06 0:28 ` Andrew Morton
2012-11-06 8:03 ` Michal Hocko
2012-11-08 11:05 ` Michal Hocko
2012-11-08 14:33 ` Michal Hocko
2012-11-07 7:04 ` Glauber Costa
2012-11-07 7:13 ` Andrew Morton
2012-11-01 12:07 ` [PATCH v6 20/29] memcg: skip memcg kmem allocations in specified code regions Glauber Costa
2012-11-06 0:33 ` Andrew Morton
2012-11-01 12:07 ` [PATCH v6 21/29] sl[au]b: always get the cache from its page in kmem_cache_free Glauber Costa
2012-11-01 12:07 ` [PATCH v6 22/29] sl[au]b: Allocate objects from memcg cache Glauber Costa
2012-11-01 12:07 ` [PATCH v6 23/29] memcg: destroy memcg caches Glauber Costa
2012-11-02 0:05 ` Andrew Morton
2012-11-02 7:46 ` Glauber Costa
2012-11-02 20:19 ` Michal Hocko
2012-11-06 0:40 ` Andrew Morton
2012-11-01 12:07 ` [PATCH v6 24/29] memcg/sl[au]b Track all the memcg children of a kmem_cache Glauber Costa
2012-11-01 12:07 ` [PATCH v6 25/29] memcg/sl[au]b: shrink dead caches Glauber Costa
2012-11-06 0:48 ` Andrew Morton
2012-11-07 7:13 ` Glauber Costa
2012-11-07 7:16 ` Andrew Morton
2012-11-07 9:22 ` Glauber Costa
2012-11-07 22:46 ` Andrew Morton
2012-11-08 7:13 ` Glauber Costa
2012-11-08 17:15 ` Christoph Lameter
2012-11-08 19:21 ` Andrew Morton [this message]
2012-11-08 22:31 ` Glauber Costa
2012-11-08 22:40 ` Andrew Morton
2012-11-09 20:06 ` Christoph Lameter
2012-11-09 20:04 ` Christoph Lameter
2012-11-01 12:07 ` [PATCH v6 26/29] Aggregate memcg cache values in slabinfo Glauber Costa
2012-11-06 0:57 ` Andrew Morton
2012-11-01 12:07 ` [PATCH v6 27/29] slab: propagate tunables values Glauber Costa
2012-11-01 12:07 ` [PATCH v6 28/29] slub: slub-specific propagation changes Glauber Costa
2012-11-06 19:25 ` Andrew Morton
2012-11-07 15:53 ` Sasha Levin
2012-11-08 6:51 ` Glauber Costa
2012-11-09 3:37 ` Sasha Levin
2012-11-14 12:06 ` Glauber Costa
2012-11-01 12:07 ` [PATCH v6 29/29] Add slab-specific documentation about the kmem controller Glauber Costa
2012-11-02 0:04 ` [PATCH v6 00/29] kmem controller for memcg Andrew Morton
2012-11-02 7:41 ` Glauber Costa
2012-11-02 19:25 ` JoonSoo Kim
2012-11-02 23:06 ` Tejun Heo
2012-11-05 8:14 ` Glauber Costa
2012-11-05 8:18 ` Glauber Costa
2012-11-03 3:36 ` Greg Thelen
2012-11-02 8:30 ` Pekka Enberg
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