Diffstat (limited to 'Documentation/cgroups/blkio-controller.txt')
1 files changed, 24 insertions, 11 deletions
diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index a794ce91a2d..da272c8f44e 100644
@@ -94,13 +94,11 @@ Throttling/Upper Limit policy
-- Currently none of the IO control policy supports hierarchical groups. But
- cgroup interface does allow creation of hierarchical cgroups and internally
- IO policies treat them as flat hierarchy.
+- Currently only CFQ supports hierarchical groups. For throttling,
+ cgroup interface does allow creation of hierarchical cgroups and
+ internally it treats them as flat hierarchy.
- So this patch will allow creation of cgroup hierarchcy but at the backend
- everything will be treated as flat. So if somebody created a hierarchy like
- as follows.
+ If somebody created a hierarchy like as follows.
@@ -108,16 +106,20 @@ Hierarchical Cgroups
- CFQ and throttling will practically treat all groups at same level.
+ CFQ will handle the hierarchy correctly but and throttling will
+ practically treat all groups at same level. For details on CFQ
+ hierarchy support, refer to Documentation/block/cfq-iosched.txt.
+ Throttling will treat the hierarchy as if it looks like the
/ / \ \
root test1 test2 test3
- Down the line we can implement hierarchical accounting/control support
- and also introduce a new cgroup file "use_hierarchy" which will control
- whether cgroup hierarchy is viewed as flat or hierarchical by the policy..
- This is how memory controller also has implemented the things.
+ Nesting cgroups, while allowed, isn't officially supported and blkio
+ genereates warning when cgroups nest. Once throttling implements
+ hierarchy support, hierarchy will be supported and the warning will
+ be removed.
Various user visible config options
@@ -172,6 +174,12 @@ Proportional weight policy files
+ - Equivalents of blkio.weight[_device] for the purpose of
+ deciding how much weight tasks in the given cgroup has while
+ competing with the cgroup's child cgroups. For details,
+ please refer to Documentation/block/cfq-iosched.txt.
- disk time allocated to cgroup per device in milliseconds. First
two fields specify the major and minor number of the device and
@@ -279,6 +287,11 @@ Proportional weight policy files
and minor number of the device and third field specifies the number
of times a group was dequeued from a particular device.
+ - Recursive version of various stats. These files show the
+ same information as their non-recursive counterparts but
+ include stats from all the descendant cgroups.
Throttling/Upper limit policy files