This patchset introduces new capability to the cgroup v2 core to give more freedom and flexibility to controllers so that they can have their own unique views of the virtual process hierarchies that can best suit thier own use cases without suffering unneeded performance problem. This patchset is derived from my previous v2 RFC patchset on https://lkml.org/lkml/2017/5/15/440 cgroup: Major changes to cgroup v2 core It is on top of Tejun's "cgroup: implement cgroup2 thread mode, v2" and my "cgroup: Make debug controller useful for debugging" patchsets: https://lkml.org/lkml/2017/6/10/93 https://lkml.org/lkml/2017/6/13/862 Patch 1 relaxes the no internal process constraint to allow internal processes if no non-threaded (resource domain) controllers are enabled. Patch 2 introduces a new bypass mode (previously called pass-through mode) that allows a controller to be disabled in the current cgroup, but re-enabled again in its children. This is enabled by writing the controller name prefixed with '#' to the "cgroup.controllers" file. A controller can be bypassed only if it is enabled in the parent's subtree_control file. Patch 3 extends the bypass mode to the "cgroup.subtree_control" file allowing a parent cgroup to enforce all its child cgroups to have a controller in bypass mode. Patch 4 introduces a new subtree root mode which restricts the number of child cgroups to one and controllers are granted to its child in bypass mode only. This mode is to be used by containers. The cgroup with subtree root mode on will control the resources passed down to its only child which will be the root of the container cgroup hierarchy. Like a real cgroup v2 root, there is no control knobs to tune the resources. Instead, all the tuning will be done in its parent. The container root can enable controllers in its child cgroups to further restrict the distribution of resources if it so desires. Like a real root, the no internal process constraint does not apply to the pseudo root and it can be a mixable root of a mixed threaded tree. Patch 5 fixes a problem discovered during testing that rapid enabling and disabling of controllers can lead to undesirable errors. Patch 6 extends the debug controller to expose additional information introduced by this patchset. Waiman Long (6): cgroup: Relax the no internal process constraint cgroup: Enable bypass mode in cgroup v2 cgroup: Allow bypss mode in subtree_control cgroup: Introduce subtree root mode cgroup: Skip dying css in cgroup_apply_control_{enable,disable} cgroup: Make debug controller display bypass and subtree root modes info Documentation/cgroup-v2.txt | 194 +++++++++++++++++---- include/linux/cgroup-defs.h | 24 +++ kernel/cgroup/cgroup-internal.h | 12 ++ kernel/cgroup/cgroup.c | 372 ++++++++++++++++++++++++++++++++-------- kernel/cgroup/debug.c | 27 ++- 5 files changed, 512 insertions(+), 117 deletions(-) -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
