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Subject[RFC][PATCH 1/4] Memory controller soft limit documentation
From: Balbir Singh <>

Add documentation for soft limit feature support.

Signed-off-by: Balbir Singh <>

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

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