Diffstat (limited to 'Documentation/cgroups/unified-hierarchy.txt')
1 files changed, 72 insertions, 8 deletions
diff --git a/Documentation/cgroups/unified-hierarchy.txt b/Documentation/cgroups/unified-hierarchy.txt
index 86847a7647ab..1ee9caf29e57 100644
@@ -23,10 +23,13 @@ CONTENTS
5. Other Changes
5-1. [Un]populated Notification
5-2. Other Core Changes
- 5-3. Per-Controller Changes
- 5-3-1. blkio
- 5-3-2. cpuset
- 5-3-3. memory
+ 5-3. Controller File Conventions
+ 5-3-1. Format
+ 5-3-2. Control Knobs
+ 5-4. Per-Controller Changes
+ 5-4-1. blkio
+ 5-4-2. cpuset
+ 5-4-3. memory
6. Planned Changes
6-1. CAP for resource control
@@ -372,14 +375,75 @@ supported and the interface files "release_agent" and
- The "cgroup.clone_children" file is removed.
-5-3. Per-Controller Changes
+5-3. Controller File Conventions
+In general, all controller files should be in one of the following
+formats whenever possible.
+- Values only files
+ VAL0 VAL1...\n
+- Flat keyed files
+ KEY0 VAL0\n
+ KEY1 VAL1\n
+- Nested keyed files
+ KEY0 SUB_KEY0=VAL00 SUB_KEY1=VAL01...
+ KEY1 SUB_KEY0=VAL10 SUB_KEY1=VAL11...
+For a writeable file, the format for writing should generally match
+reading; however, controllers may allow omitting later fields or
+implement restricted shortcuts for most common use cases.
+For both flat and nested keyed files, only the values for a single key
+can be written at a time. For nested keyed files, the sub key pairs
+may be specified in any order and not all pairs have to be specified.
+5-3-2. Control Knobs
+- Settings for a single feature should generally be implemented in a
+ single file.
+- In general, the root cgroup should be exempt from resource control
+ and thus shouldn't have resource control knobs.
+- If a controller implements ratio based resource distribution, the
+ control knob should be named "weight" and have the range [1, 10000]
+ and 100 should be the default value. The values are chosen to allow
+ enough and symmetric bias in both directions while keeping it
+ intuitive (the default is 100%).
+- If a controller implements an absolute resource guarantee and/or
+ limit, the control knobs should be named "min" and "max"
+ respectively. If a controller implements best effort resource
+ gurantee and/or limit, the control knobs should be named "low" and
+ "high" respectively.
+ In the above four control files, the special token "max" should be
+ used to represent upward infinity for both reading and writing.
+- If a setting has configurable default value and specific overrides,
+ the default settings should be keyed with "default" and appear as
+ the first entry in the file. Specific entries can use "default" as
+ its value to indicate inheritance of the default value.
+5-4. Per-Controller Changes
- blk-throttle becomes properly hierarchical.
- Tasks are kept in empty cpusets after hotplug and take on the masks
of the nearest non-empty ancestor, instead of being moved to it.
@@ -388,7 +452,7 @@ supported and the interface files "release_agent" and
masks of the nearest non-empty ancestor.
- use_hierarchy is on by default and the cgroup file for the flag is