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


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