diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/cgroups/blkio-controller.txt | 29 |
1 files changed, 15 insertions, 14 deletions
diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt index da272c8f44e..cd556b91478 100644 --- a/Documentation/cgroups/blkio-controller.txt +++ b/Documentation/cgroups/blkio-controller.txt @@ -94,11 +94,13 @@ Throttling/Upper Limit policy Hierarchical Cgroups ==================== -- Currently only CFQ supports hierarchical groups. For throttling, - cgroup interface does allow creation of hierarchical cgroups and - internally it treats them as flat hierarchy. - If somebody created a hierarchy like as follows. +Both CFQ and throttling implement hierarchy support; however, +throttling's hierarchy support is enabled iff "sane_behavior" is +enabled from cgroup side, which currently is a development option and +not publicly available. + +If somebody created a hierarchy like as follows. root / \ @@ -106,21 +108,20 @@ Hierarchical Cgroups | test3 - 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 - following. +CFQ by default and throttling with "sane_behavior" will handle the +hierarchy correctly. For details on CFQ hierarchy support, refer to +Documentation/block/cfq-iosched.txt. For throttling, all limits apply +to the whole subtree while all statistics are local to the IOs +directly generated by tasks in that cgroup. + +Throttling without "sane_behavior" enabled from cgroup side will +practically treat all groups at same level as if it looks like the +following. pivot / / \ \ root test1 test2 test3 - 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 =================================== CONFIG_BLK_CGROUP |