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From: Andrew Morton <akpm@linux-foundation.org>
To: Glauber Costa <glommer@parallels.com>
Cc: <linux-mm@kvack.org>, <cgroups@vger.kernel.org>,
	Mel Gorman <mgorman@suse.de>, Tejun Heo <tj@kernel.org>,
	Michal Hocko <mhocko@suse.cz>,
	Johannes Weiner <hannes@cmpxchg.org>,
	<kamezawa.hiroyu@jp.fujitsu.com>,
	Christoph Lameter <cl@linux.com>,
	David Rientjes <rientjes@google.com>,
	Pekka Enberg <penberg@kernel.org>, <devel@openvz.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 00/14] kmem controller for memcg.
Date: Wed, 17 Oct 2012 15:11:42 -0700	[thread overview]
Message-ID: <20121017151142.71e1f3c5.akpm@linux-foundation.org> (raw)
In-Reply-To: <1350382611-20579-1-git-send-email-glommer@parallels.com>

On Tue, 16 Oct 2012 14:16:37 +0400
Glauber Costa <glommer@parallels.com> wrote:

> ...
>
> A general explanation of what this is all about follows:
> 
> The kernel memory limitation mechanism for memcg concerns itself with
> disallowing potentially non-reclaimable allocations to happen in exaggerate
> quantities by a particular set of processes (cgroup). Those allocations could
> create pressure that affects the behavior of a different and unrelated set of
> processes.
> 
> Its basic working mechanism is to annotate some allocations with the
> _GFP_KMEMCG flag. When this flag is set, the current process allocating will
> have its memcg identified and charged against. When reaching a specific limit,
> further allocations will be denied.

The need to set _GFP_KMEMCG is rather unpleasing, and makes one wonder
"why didn't it just track all allocations".

Does this mean that over time we can expect more sites to get the
_GFP_KMEMCG tagging?  If so, are there any special implications, or do
we just go in, do the one-line patch and expect everything to work?  If
so, why don't we go in and do that tagging right now?

And how *accurate* is the proposed code?  What percentage of kernel
memory allocations are unaccounted, typical case and worst case?

All sorts of questions come to mind over this decision, but it was
unexplained.  It should be, please.  A lot!

>
> ...
> 
> Limits lower than
> the user limit effectively means there is a separate kernel memory limit that
> may be reached independently than the user limit. Values equal or greater than
> the user limit implies only that kernel memory is tracked. This provides a
> unified vision of "maximum memory", be it kernel or user memory.
>

I'm struggling to understand that text much at all.  Reading the
Documentation/cgroups/memory.txt patch helped.


  parent reply	other threads:[~2012-10-17 22:11 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
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 ` Andrew Morton [this message]
2012-10-18 16:51   ` [PATCH v5 00/14] kmem controller for memcg Glauber Costa
2012-10-18 19:21     ` Andrew Morton
2012-10-19  9:55       ` Glauber Costa

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