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-rw-r--r--Documentation/cgroups/unified-hierarchy.txt61
1 files changed, 57 insertions, 4 deletions
diff --git a/Documentation/cgroups/unified-hierarchy.txt b/Documentation/cgroups/unified-hierarchy.txt
index 1ee9caf29e57..bd1ce15d5178 100644
--- a/Documentation/cgroups/unified-hierarchy.txt
+++ b/Documentation/cgroups/unified-hierarchy.txt
@@ -27,7 +27,7 @@ CONTENTS
5-3-1. Format
5-3-2. Control Knobs
5-4. Per-Controller Changes
- 5-4-1. blkio
+ 5-4-1. io
5-4-2. cpuset
5-4-3. memory
6. Planned Changes
@@ -203,7 +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
@@ -438,9 +438,62 @@ may be specified in any order and not all pairs have to be specified.
5-4. Per-Controller Changes
-5-4-1. blkio
+5-4-1. io
-- blk-throttle becomes properly hierarchical.
+- 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 10 and 1000 and defaults to 500. 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