linux-kernel - [RFC][PATCH 1/4] Memory controller soft limit documentation

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Message-Id: <20090107184116.18062.8379.sendpatchset@localhost.localdomain>
Date:	Thu, 08 Jan 2009 00:11:16 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
	YAMAMOTO Takashi <yamamoto@...inux.co.jp>,
	Paul Menage <menage@...gle.com>, lizf@...fujitsu.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	David Rientjes <rientjes@...gle.com>,
	Pavel Emelianov <xemul@...nvz.org>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: [RFC][PATCH 1/4] Memory controller soft limit documentation

From: Balbir Singh <balbir@...ux.vnet.ibm.com>

Add documentation for soft limit feature support.

Signed-off-by: Balbir Singh <balbir@...ux.vnet.ibm.com>
---

 Documentation/controllers/memory.txt |   28 ++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff -puN Documentation/controllers/memory.txt~memcg-soft-limit-documentation Documentation/controllers/memory.txt
--- a/Documentation/controllers/memory.txt~memcg-soft-limit-documentation
+++ a/Documentation/controllers/memory.txt
@@ -360,7 +360,33 @@ cgroups created below it.
 
 NOTE2: This feature can be enabled/disabled per subtree.
 
-7. TODO
+7. Soft limits
+
+Soft limits allow for greater sharing of memory. The idea behind soft limits
+is to allow control groups to use as much of the memory as needed, provided
+
+a. There is no memory contention
+b. They do not exceed their hard limit
+
+When the system detects memory contention (through do_try_to_free_pages(),
+while allocating), control groups are pushed back to their soft limits if
+possible. If the soft limit of each control group is very high, they are
+pushed back as much as possible to make sure that one control group does not
+starve the others.
+
+7.1 Interface
+
+Soft limits can be setup by using the following commands (in this example we
+assume a soft limit of 256 megabytes)
+
+# echo 256M > memory.soft_limit_in_bytes
+
+If we want to change this to 1G, we can at any time use
+
+# echo 1G > memory.soft_limit_in_bytes
+
+
+8. TODO
 
 1. Add support for accounting huge pages (as a separate controller)
 2. Make per-cgroup scanner reclaim not-shared pages first
_

-- 
	Balbir
--
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