From: Aristeu Rozanski <aris@ruivo.org>
To: Christoph Lameter <cl@linux.com>
Cc: Glauber Costa <glommer@parallels.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
Mel Gorman <mgorman@suse.de>, Tejun Heo <tj@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>,
Johannes Weiner <hannes@cmpxchg.org>,
kamezawa.hiroyu@jp.fujitsu.com,
David Rientjes <rientjes@google.com>,
Pekka Enberg <penberg@kernel.org>,
devel@openvz.org, linux-kernel@vger.kernel.org,
Frederic Weisbecker <fweisbec@redhat.com>,
Pekka Enberg <penberg@cs.helsinki.fi>,
Suleiman Souhlal <suleiman@google.com>
Subject: Re: [PATCH v5 14/14] Add documentation about the kmem controller
Date: Tue, 16 Oct 2012 14:55:42 -0400 [thread overview]
Message-ID: <20121016185542.GA5423@cathedrallabs.org> (raw)
In-Reply-To: <0000013a6ad26c73-d043cf97-c44a-45c1-9cae-0a962e93a005-000000@email.amazonses.com>
On Tue, Oct 16, 2012 at 06:25:06PM +0000, Christoph Lameter wrote:
> On Tue, 16 Oct 2012, Glauber Costa wrote:
>
> >
> > + memory.kmem.limit_in_bytes # set/show hard limit for kernel memory
> > + memory.kmem.usage_in_bytes # show current kernel memory allocation
> > + memory.kmem.failcnt # show the number of kernel memory usage hits limits
> > + memory.kmem.max_usage_in_bytes # show max kernel memory usage recorded
>
> Does it actually make sense to limit kernel memory? The user generally has
> no idea how much kernel memory a process is using and kernel changes can
> change the memory footprint. Given the fuzzy accounting in the kernel a
> large cache refill (if someone configures the slab batch count to be
> really big f.e.) can account a lot of memory to the wrong cgroup. The
> allocation could fail.
>
> Limiting the total memory use of a process (U+K) would make more sense I
> guess. Only U is probably sufficient? In what way would a limitation on
> kernel memory in use be good?
It's about preventing abuses caused by bugs or malicious use and avoiding
groups stepping on each others' toes. You're saying that letting a group
to allocate 32GB of paged memory is the same as 32GB of kernel memory?
I don't belive sysadmins will keep a tight limit for kernel memory but rather
a safety limit in case something goes wrong. usage_in_bytes will provide
data to get the limits better adjusted.
The innacuracy of the kmem accounting is (AFAIK) a cost tradeoff.
--
Aristeu
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next prev parent reply other threads:[~2012-10-16 18:56 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-16 10:16 [PATCH v5 00/14] kmem controller for memcg Glauber Costa
2012-10-16 10:16 ` [PATCH v5 01/14] memcg: Make it possible to use the stock for more than one page Glauber Costa
2012-10-17 22:11 ` Andrew Morton
2012-10-18 16:54 ` Glauber Costa
2012-10-16 10:16 ` [PATCH v5 02/14] memcg: Reclaim when more than one page needed Glauber Costa
2012-10-17 21:46 ` David Rientjes
2012-10-16 10:16 ` [PATCH v5 03/14] memcg: change defines to an enum Glauber Costa
2012-10-17 21:50 ` David Rientjes
2012-10-16 10:16 ` [PATCH v5 04/14] kmem accounting basic infrastructure Glauber Costa
2012-10-16 12:14 ` Michal Hocko
2012-10-17 22:08 ` David Rientjes
2012-10-18 17:01 ` Glauber Costa
2012-10-18 19:47 ` Tejun Heo
2012-10-18 19:37 ` Tejun Heo
2012-10-17 22:12 ` Andrew Morton
2012-10-18 17:03 ` Glauber Costa
2012-10-16 10:16 ` [PATCH v5 05/14] Add a __GFP_KMEMCG flag Glauber Costa
2012-10-16 12:15 ` Michal Hocko
2012-10-17 22:09 ` David Rientjes
2012-10-16 10:16 ` [PATCH v5 06/14] memcg: kmem controller infrastructure Glauber Costa
2012-10-17 6:40 ` Kamezawa Hiroyuki
2012-10-17 22:12 ` Andrew Morton
2012-10-18 9:16 ` Glauber Costa
2012-10-18 22:06 ` David Rientjes
2012-10-19 9:10 ` Glauber Costa
2012-10-19 9:31 ` David Rientjes
2012-10-19 10:00 ` Glauber Costa
2012-10-17 22:37 ` David Rientjes
2012-10-18 9:23 ` Glauber Costa
2012-10-18 21:59 ` David Rientjes
2012-10-19 10:08 ` Glauber Costa
2012-10-19 20:34 ` David Rientjes
2012-10-22 12:34 ` Glauber Costa
2012-10-22 12:51 ` Michal Hocko
2012-10-22 12:52 ` Glauber Costa
2012-10-16 10:16 ` [PATCH v5 07/14] mm: Allocate kernel pages to the right memcg Glauber Costa
2012-10-16 15:31 ` Christoph Lameter
2012-10-16 18:55 ` Glauber Costa
2012-10-17 22:12 ` Andrew Morton
2012-10-18 9:24 ` Glauber Costa
2012-10-18 20:44 ` Andrew Morton
2012-10-18 11:53 ` Glauber Costa
2012-10-17 22:43 ` David Rientjes
2012-10-16 10:16 ` [PATCH v5 08/14] res_counter: return amount of charges after res_counter_uncharge Glauber Costa
2012-10-17 23:23 ` David Rientjes
2012-10-16 10:16 ` [PATCH v5 09/14] memcg: kmem accounting lifecycle management Glauber Costa
2012-10-17 23:28 ` David Rientjes
2012-10-18 6:14 ` Michal Hocko
2012-10-18 9:42 ` Glauber Costa
2012-10-16 10:16 ` [PATCH v5 10/14] memcg: use static branches when code not in use Glauber Costa
2012-10-16 10:16 ` [PATCH v5 11/14] memcg: allow a memcg with kmem charges to be destructed Glauber Costa
2012-10-17 22:12 ` Andrew Morton
2012-10-18 9:33 ` Glauber Costa
2012-10-16 10:16 ` [PATCH v5 12/14] execute the whole memcg freeing in free_worker Glauber Costa
2012-10-17 6:56 ` Kamezawa Hiroyuki
2012-10-16 10:16 ` [PATCH v5 13/14] protect architectures where THREAD_SIZE >= PAGE_SIZE against fork bombs Glauber Costa
2012-10-17 22:12 ` Andrew Morton
2012-10-18 9:37 ` Glauber Costa
2012-10-16 10:16 ` [PATCH v5 14/14] Add documentation about the kmem controller Glauber Costa
2012-10-16 12:23 ` Michal Hocko
2012-10-16 18:25 ` Christoph Lameter
2012-10-16 18:55 ` Aristeu Rozanski [this message]
2012-10-16 19:02 ` Glauber Costa
2012-10-16 19:30 ` Christoph Lameter
2012-10-17 22:12 ` Andrew Morton
2012-10-18 9:38 ` Glauber Costa
2012-10-17 22:11 ` [PATCH v5 00/14] kmem controller for memcg Andrew Morton
2012-10-18 16:51 ` Glauber Costa
2012-10-18 19:21 ` Andrew Morton
2012-10-19 9:55 ` Glauber Costa
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