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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-12-15 14:52:16 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-12-15 14:52:16 -0300
commit8d91c1e411f55d7ea91b1183a2e9f8088fb4d5be (patch)
treee9891aa6c295060d065adffd610c4f49ecf884f3 /Documentation/cgroups/unified-hierarchy.txt
parenta71852147516bc1cb5b0b3cbd13639bfd4022dc8 (diff)
Linux-libre 4.3.2-gnu
Diffstat (limited to 'Documentation/cgroups/unified-hierarchy.txt')
-rw-r--r--Documentation/cgroups/unified-hierarchy.txt137
1 files changed, 127 insertions, 10 deletions
diff --git a/Documentation/cgroups/unified-hierarchy.txt b/Documentation/cgroups/unified-hierarchy.txt
index 86847a764..e0975c2cf 100644
--- a/Documentation/cgroups/unified-hierarchy.txt
+++ b/Documentation/cgroups/unified-hierarchy.txt
@@ -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. io
+ 5-4-2. cpuset
+ 5-4-3. memory
6. Planned Changes
6-1. CAP for resource control
@@ -200,7 +203,7 @@ other issues. The mapping from nice level to weight isn't obvious or
universal, and there are various other knobs which simply aren't
available for tasks.
-The blkio controller implicitly creates a hidden leaf node for each
+The io controller implicitly creates a hidden leaf node for each
cgroup to host the tasks. The hidden leaf has its own copies of all
the knobs with "leaf_" prefixed. While this allows equivalent control
over internal tasks, it's with serious drawbacks. It always adds an
@@ -372,14 +375,128 @@ 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
-5-3-1. blkio
+5-3-1. Format
-- blk-throttle becomes properly hierarchical.
+In general, all controller files should be in one of the following
+formats whenever possible.
+- Values only files
-5-3-2. cpuset
+ 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
+
+5-4-1. io
+
+- blkio is renamed to io. The interface is overhauled anyway. The
+ new name is more in line with the other two major controllers, cpu
+ and memory, and better suited given that it may be used for cgroup
+ writeback without involving block layer.
+
+- Everything including stat is always hierarchical making separate
+ recursive stat files pointless and, as no internal node can have
+ tasks, leaf weights are meaningless. The operation model is
+ simplified and the interface is overhauled accordingly.
+
+ io.stat
+
+ The stat file. The reported stats are from the point where
+ bio's are issued to request_queue. The stats are counted
+ independent of which policies are enabled. Each line in the
+ file follows the following format. More fields may later be
+ added at the end.
+
+ $MAJ:$MIN rbytes=$RBYTES wbytes=$WBYTES rios=$RIOS wrios=$WIOS
+
+ io.weight
+
+ The weight setting, currently only available and effective if
+ cfq-iosched is in use for the target device. The weight is
+ between 1 and 10000 and defaults to 100. The first line
+ always contains the default weight in the following format to
+ use when per-device setting is missing.
+
+ default $WEIGHT
+
+ Subsequent lines list per-device weights of the following
+ format.
+
+ $MAJ:$MIN $WEIGHT
+
+ Writing "$WEIGHT" or "default $WEIGHT" changes the default
+ setting. Writing "$MAJ:$MIN $WEIGHT" sets per-device weight
+ while "$MAJ:$MIN default" clears it.
+
+ This file is available only on non-root cgroups.
+
+ io.max
+
+ The maximum bandwidth and/or iops setting, only available if
+ blk-throttle is enabled. The file is of the following format.
+
+ $MAJ:$MIN rbps=$RBPS wbps=$WBPS riops=$RIOPS wiops=$WIOPS
+
+ ${R|W}BPS are read/write bytes per second and ${R|W}IOPS are
+ read/write IOs per second. "max" indicates no limit. Writing
+ to the file follows the same format but the individual
+ settings may be ommitted or specified in any order.
+
+ This file is available only on non-root cgroups.
+
+
+5-4-2. cpuset
- 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 +505,7 @@ supported and the interface files "release_agent" and
masks of the nearest non-empty ancestor.
-5-3-3. memory
+5-4-3. memory
- use_hierarchy is on by default and the cgroup file for the flag is
not created.