Merge remote-tracking branch 'percpu/for-next'

[karo-tx-linux.git] / Documentation / cgroups / unified-hierarchy.txt

diff --git a/Documentation/cgroups/unified-hierarchy.txt b/Documentation/cgroups/unified-hierarchy.txt
index 1ee9caf29e576c0a8a89927fb9cced2ed5521c60..5c07337b51c1b345483f4ba2699e6ce8b7ea2616 100644 (file)
--- 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 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 omitted or specified in any order.
+
+       This file is available only on non-root cgroups.
 
 
 5-4-2. cpuset