From: Michal Hocko <mhocko@suse.cz>
To: Glauber Costa <glommer@parallels.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>,
Suleiman Souhlal <suleiman@google.com>, Tejun Heo <tj@kernel.org>,
cgroups@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com,
Johannes Weiner <hannes@cmpxchg.org>,
Greg Thelen <gthelen@google.com>,
devel@openvz.org, Frederic Weisbecker <fweisbec@gmail.com>,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@cs.helsinki.fi>
Subject: Re: [PATCH v4 10/14] memcg: use static branches when code not in use
Date: Thu, 11 Oct 2012 15:40:28 +0200 [thread overview]
Message-ID: <20121011134028.GH29295@dhcp22.suse.cz> (raw)
In-Reply-To: <1349690780-15988-11-git-send-email-glommer@parallels.com>
On Mon 08-10-12 14:06:16, Glauber Costa wrote:
> We can use static branches to patch the code in or out when not used.
>
> Because the _ACTIVE bit on kmem_accounted is only set after the
> increment is done, we guarantee that the root memcg will always be
> selected for kmem charges until all call sites are patched (see
> memcg_kmem_enabled). This guarantees that no mischarges are applied.
>
> static branch decrement happens when the last reference count from the
> kmem accounting in memcg dies. This will only happen when the charges
> drop down to 0.
>
> When that happen, we need to disable the static branch only on those
> memcgs that enabled it. To achieve this, we would be forced to
> complicate the code by keeping track of which memcgs were the ones
> that actually enabled limits, and which ones got it from its parents.
>
> It is a lot simpler just to do static_key_slow_inc() on every child
> that is accounted.
>
> [ v4: adapted this patch to the changes in kmem_accounted ]
>
> Signed-off-by: Glauber Costa <glommer@parallels.com>
> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> CC: Christoph Lameter <cl@linux.com>
> CC: Pekka Enberg <penberg@cs.helsinki.fi>
> CC: Michal Hocko <mhocko@suse.cz>
> CC: Johannes Weiner <hannes@cmpxchg.org>
> CC: Suleiman Souhlal <suleiman@google.com>
Looks reasonable to me
Acked-by: Michal Hocko <mhocko@suse.cz>
Just a little nit.
[...]
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 634c7b5..724a08b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -344,11 +344,15 @@ struct mem_cgroup {
> /* internal only representation about the status of kmem accounting. */
> enum {
> KMEM_ACCOUNTED_ACTIVE = 0, /* accounted by this cgroup itself */
> + KMEM_ACCOUNTED_ACTIVATED, /* static key enabled. */
> KMEM_ACCOUNTED_DEAD, /* dead memcg, pending kmem charges */
> };
>
> -/* first bit */
> -#define KMEM_ACCOUNTED_MASK 0x1
> +/*
> + * first two bits. We account when limit is on, but only after
> + * call sites are patched
> + */
> +#define KMEM_ACCOUNTED_MASK 0x3
The names are long but why not use KMEM_ACCOUNTED_ACTIVE*
#define KMEM_ACCOUNTED_MASK 1<<KMEM_ACCOUNTED_ACTIVE | 1<<KMEM_ACCOUNTED_ACTIVATED
[...]
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2012-10-11 13:40 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-08 10:06 [PATCH v4 00/14] kmem controller for memcg Glauber Costa
2012-10-08 10:06 ` [PATCH v4 01/14] memcg: Make it possible to use the stock for more than one page Glauber Costa
2012-10-08 10:06 ` [PATCH v4 02/14] memcg: Reclaim when more than one page needed Glauber Costa
2012-10-16 3:22 ` Kamezawa Hiroyuki
2012-10-08 10:06 ` [PATCH v4 03/14] memcg: change defines to an enum Glauber Costa
2012-10-08 10:06 ` [PATCH v4 04/14] kmem accounting basic infrastructure Glauber Costa
2012-10-11 10:11 ` Michal Hocko
2012-10-11 12:53 ` Michal Hocko
2012-10-11 13:38 ` Michal Hocko
2012-10-12 7:36 ` Glauber Costa
2012-10-12 8:27 ` Michal Hocko
2012-10-08 10:06 ` [PATCH v4 05/14] Add a __GFP_KMEMCG flag Glauber Costa
2012-10-09 15:04 ` Michal Hocko
2012-10-08 10:06 ` [PATCH v4 06/14] memcg: kmem controller infrastructure Glauber Costa
2012-10-11 12:42 ` Michal Hocko
2012-10-11 12:56 ` Michal Hocko
2012-10-12 7:45 ` Glauber Costa
2012-10-12 8:39 ` Michal Hocko
2012-10-12 8:44 ` Glauber Costa
2012-10-12 8:57 ` Michal Hocko
2012-10-12 9:13 ` Glauber Costa
2012-10-12 9:47 ` Michal Hocko
2012-10-16 8:00 ` Kamezawa Hiroyuki
2012-10-08 10:06 ` [PATCH v4 07/14] mm: Allocate kernel pages to the right memcg Glauber Costa
2012-10-08 10:06 ` [PATCH v4 08/14] res_counter: return amount of charges after res_counter_uncharge Glauber Costa
2012-10-09 15:08 ` Michal Hocko
2012-10-09 15:14 ` Glauber Costa
2012-10-09 15:35 ` Michal Hocko
2012-10-10 9:03 ` Glauber Costa
2012-10-10 11:24 ` Michal Hocko
2012-10-10 11:25 ` Michal Hocko
2012-10-16 8:20 ` Kamezawa Hiroyuki
2012-10-08 10:06 ` [PATCH v4 09/14] memcg: kmem accounting lifecycle management Glauber Costa
2012-10-11 13:11 ` Michal Hocko
2012-10-12 7:47 ` Glauber Costa
2012-10-12 8:41 ` Michal Hocko
2012-10-16 8:41 ` Kamezawa Hiroyuki
2012-10-08 10:06 ` [PATCH v4 10/14] memcg: use static branches when code not in use Glauber Costa
2012-10-11 13:40 ` Michal Hocko [this message]
2012-10-12 7:47 ` Glauber Costa
2012-10-16 8:48 ` Kamezawa Hiroyuki
2012-10-08 10:06 ` [PATCH v4 11/14] memcg: allow a memcg with kmem charges to be destructed Glauber Costa
2012-10-08 10:06 ` [PATCH v4 12/14] execute the whole memcg freeing in free_worker Glauber Costa
2012-10-11 14:21 ` Michal Hocko
2012-10-08 10:06 ` [PATCH v4 13/14] protect architectures where THREAD_SIZE >= PAGE_SIZE against fork bombs Glauber Costa
2012-10-08 10:06 ` [PATCH v4 14/14] Add documentation about the kmem controller Glauber Costa
2012-10-11 14:35 ` Michal Hocko
2012-10-12 7:53 ` Glauber Costa
2012-10-12 8:44 ` Michal Hocko
2012-10-17 7:29 ` Kamezawa Hiroyuki
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