[PATCH -V6 14/14] memcg: Add memory controller documentation for hugetlb management

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 Documentation/cgroups/memory.txt |   29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 4c95c00..d99c41b 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -43,6 +43,7 @@ Features:
  - usage threshold notifier
  - oom-killer disable knob and oom-notifier
  - Root cgroup has no limit controls.
+ - resource accounting for HugeTLB pages
 
  Kernel memory support is work in progress, and the current version provides
  basically functionality. (See Section 2.7)
@@ -75,6 +76,12 @@ Brief summary of control files.
  memory.kmem.tcp.limit_in_bytes  # set/show hard limit for tcp buf memory
  memory.kmem.tcp.usage_in_bytes  # show current tcp buf memory allocation
 
+
+ memory.hugetlb.<hugepagesize>.limit_in_bytes     # set/show limit of "hugepagesize" hugetlb usage
+ memory.hugetlb.<hugepagesize>.max_usage_in_bytes # show max "hugepagesize" hugetlb  usage recorded
+ memory.hugetlb.<hugepagesize>.usage_in_bytes     # show current res_counter usage for "hugepagesize" hugetlb
+						  # see 5.7 for details
+
 1. History
 
 The memory controller has a long history. A request for comments for the memory
@@ -279,6 +286,15 @@ per cgroup, instead of globally.
 
 * tcp memory pressure: sockets memory pressure for the tcp protocol.
 
+2.8 HugeTLB extension
+
+This extension allows to limit the HugeTLB usage per control group and
+enforces the controller limit during page fault. Since HugeTLB doesn't
+support page reclaim, enforcing the limit at page fault time implies that,
+the application will get SIGBUS signal if it tries to access HugeTLB pages
+beyond its limit. This requires the application to know beforehand how much
+HugeTLB pages it would require for its use.
+
 3. User Interface
 
 0. Configuration
@@ -287,6 +303,7 @@ a. Enable CONFIG_CGROUPS
 b. Enable CONFIG_RESOURCE_COUNTERS
 c. Enable CONFIG_CGROUP_MEM_RES_CTLR
 d. Enable CONFIG_CGROUP_MEM_RES_CTLR_SWAP (to use swap extension)
+f. Enable CONFIG_MEM_RES_CTLR_HUGETLB (to use HugeTLB extension)
 
 1. Prepare the cgroups (see cgroups.txt, Why are cgroups needed?)
 # mount -t tmpfs none /sys/fs/cgroup
@@ -510,6 +527,18 @@ unevictable=<total anon pages> N0=<node 0 pages> N1=<node 1 pages> ...
 
 And we have total = file + anon + unevictable.
 
+5.7 HugeTLB resource control files
+For a system supporting two hugepage size (16M and 16G) the control
+files include:
+
+ memory.hugetlb.16GB.limit_in_bytes
+ memory.hugetlb.16GB.max_usage_in_bytes
+ memory.hugetlb.16GB.usage_in_bytes
+ memory.hugetlb.16MB.limit_in_bytes
+ memory.hugetlb.16MB.max_usage_in_bytes
+ memory.hugetlb.16MB.usage_in_bytes
+
+
 6. Hierarchy support
 
 The memory controller supports a deep hierarchy and hierarchical accounting.
-- 
1.7.10