v2->v3: - Remove invalid cgroup subdirectory creation patch. - Add use cases for the bypass mode and removing statements about control files ownership in cgroup-v2.txt. - Restrict bypass mode to non-domain (threaded) controllers only.
v1->v2: - Remove relax no-internal-process constraint patch as this feature is in the thread mode v4 patch. - Remove subtree root mode patch. - Remove the skip dying css patch as I can no longer reproduce the problem. - Rework the bypass mode so that write to "cgroup.controllers" to enable or disable controller interface files is only allowed if the parent grants bypass mode to children by writing the '#'-prefixed controller to "cgroup.subtree_control". - Add a patch to disable subdirectory creation on an invalid domain. v1 patch - https://lkml.org/lkml/2017/6/14/551 v2 patch - https://lkml.org/lkml/2017/7/21/606 This patchset introduces new capability to the cgroup v2 core to give more freedom and flexibility to non-domain controllers so that they can shape their own unique views of the virtual cgroup hierarchies that can best suit thier own use cases. It also enables a cgroup parent to selectively enable a non-domain controller in a subset of its child cgroups instead of in either all or none of them. The bypass mode cannot be used on domain controllers as it will complicate resource distribution model and rules. One use case is an application that want to use cpuset, for example, to bind some worker threads to individual cpus. At the same time, the application may also want to use cpu controller to limit the amount of cpu consumed by some other threads. Right now, the only way to do that with the current v2 control scheme is to create child cgroups with both cpu and cpuset controllers enabled and put the desired processes or threads into those child cgroups. The cost of enabling cpuset on a task that need cpu controller is negligible. However, the cost of enabling cpu controller on tasks that only need cpuset can be noticeable. The performance difference may become a concern for users who are thinking of moving from cgroup v1 to v2. Similarly, instead of cpuset, if we want to use perf_event, freezer or other non-domain controllers in a subset of tasks, we will also need to enable CPU controller along with the associated performance cost. With bypass mode, we will have the ability to enable just the non-domain controllers the tasks needed in their respective child cgroups. It is just like what we can currently do with cgroup v1. This patchset is layered on top of the "for-4.14" branch of Tejun's cgroup git tree. Patch 1 introduces a new bypass mode that allows a non-domain controller to be disabled in a cgroup, but re-enabled again in its children. This is enabled by writing the controller name prefixed with '#' to the "cgroup.subtree_control" file. Then all its children will have this controller in bypass mode. Patch 2 extends the bypass mode mechanism to allow those child cgroups that are put into the bypass mode for a particular non-domain controller by their parent to be re-enabled again by writing the controller name with the '+' prefix to the "cgroup.controllers" file. Patch 3 extends the debug controller to expose additional controller masks introduced by this patchset. Waiman Long (3): cgroup: subtree_control bypass mode for non-domain controllers cgroup: Allow reenabling of controller in bypass mode cgroup: Make debug controller report new controller masks Documentation/cgroup-v2.txt | 58 +++++++--- include/linux/cgroup-defs.h | 19 +++- kernel/cgroup/cgroup.c | 250 +++++++++++++++++++++++++++++++++++--------- kernel/cgroup/debug.c | 2 + 4 files changed, 257 insertions(+), 72 deletions(-) -- 184.108.40.206 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html