[mm] [PATCH 4/4] Add soft limit documentation v2

Balbir Singh
2008-02-19T07:08:30Z

Add documentation for the soft limit feature.

Changelog v2 (Thanks to the review by Randy Dunlap)
1. Change several misuses of it's to its
2. Fix spelling errors and punctuation

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

Documentation/controllers/memory.txt | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)

diff -puN Documentation/controllers/memory.txt~memory-controller-add-soft-limit-documentation Documentation/controllers/memory.txt
--- linux-2.6.25-rc2/Documentation/controllers/memory.txt~memory-controller-add-soft-limit-documentation 2008-02-19 12:31:53.000000000 +0530
+++ linux-2.6.25-rc2-balbir/Documentation/controllers/memory.txt 2008-02-19 12:31:53.000000000 +0530
@@ -201,6 +201,22 @@ The memory.force_empty gives an interfac

will drop all charges in cgroup. Currently, this is maintained for test.

+The file memory.soft_limit_in_bytes allows users to set soft limits. A soft
+limit is set in a manner similar to limit. The limit feature described
+earlier is a hard limit. A group can never exceed its hard limit. A soft
+limit on the other hand can be exceeded. A group will be shrunk back
+to its soft limit, when there is memory pressure/contention.
+
+Ideally the soft limit should always be set to a value smaller than the
+hard limit. However, the code does not force the user to do so. The soft
+limit can be greater than the hard limit; then the soft limit has
+no meaning in that setup, since the group will always be restrained to its
+hard limit.
+
+Example setting of soft limit
+
+# echo -n 100M > memory.soft_limit_in_bytes
+
4. Testing

Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11].
@@ -221,7 +237,7 @@ some of the pages cached in the cgroup (

4.2 Task migration

-When a task migrates from one cgroup to another, it's charge is not
+When a task migrates from one cgroup to another, its charge is not
carried forward. The pages allocated from the original cgroup still
remain charged to it, the charge is dropped when the page is freed or
reclaimed.
_