linux-kernel - [patch 08/11] mm, memcg: add memcg oom reserve documentation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.02.1403041956250.8067@chino.kir.corp.google.com>
Date:	Tue, 4 Mar 2014 19:59:32 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>, Tejun Heo <tj@...nel.org>,
	Mel Gorman <mgorman@...e.de>, Oleg Nesterov <oleg@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Jianguo Wu <wujianguo@...wei.com>,
	Tim Hockin <thockin@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, cgroups@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: [patch 08/11] mm, memcg: add memcg oom reserve documentation

Add documentation on memcg oom reserves to
Documentation/cgroups/memory.txt and give an example of its usage and
recommended best practices.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 Documentation/cgroups/memory.txt | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -71,6 +71,7 @@ Brief summary of control files.
 				 (See sysctl's vm.swappiness)
  memory.move_charge_at_immigrate # set/show controls of moving charges
  memory.oom_control		 # set/show oom controls.
+ memory.oom_reserve_in_bytes	 # set/show limit of oom memory reserves
  memory.numa_stat		 # show the number of memory usage per numa node
 
  memory.kmem.limit_in_bytes      # set/show hard limit for kernel memory
@@ -772,6 +773,31 @@ At reading, current status of OOM is shown.
 	under_oom	 0 or 1 (if 1, the memory cgroup is under OOM, tasks may
 				 be stopped.)
 
+Processes that handle oom conditions in their own memcgs or their child
+memcgs may need to allocate memory themselves to do anything useful,
+including pagefaulting its text or allocating kernel memory to read the
+memcg "tasks" file.  For this reason, memory.oom_reserve_in_bytes is
+provided that specifies how much memory that processes waiting on
+memory.oom_control can allocate above the memcg limit.
+
+The memcg that the oom handler is attached to is charged for the memory
+that it allocates against its own memory.oom_reserve_in_bytes.  This
+memory is therefore only available to processes that are waiting for
+a notification.
+
+For example, if you do
+
+	# echo 2m > memory.oom_reserve_in_bytes
+
+then any process attached to this memcg that is waiting on memcg oom
+notifications anywhere on the system can allocate an additional 2MB
+above memory.limit_in_bytes.
+
+You may still consider doing mlockall(MCL_FUTURE) for processes that
+are waiting on oom notifications to keep this vaue as minimal as
+possible, or allow it to be large enough so that its text can still
+be pagefaulted in under oom conditions when the value is known.
+
 11. Memory Pressure
 
 The pressure level notifications can be used to monitor the memory
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/