[CC += linux-api@xxxxxxxxxxxxxxx] Hi Waiman, Since this is a kernel-user-space API change, for all future iterations of this patch, please CC linux-api@. The kernel source file Documentation/SubmitChecklist notes that all Linux kernel patches that change userspace interfaces should be CCed to linux-api@xxxxxxxxxxxxxxx, so that the various parties who are interested in API changes are informed. For further information, see https://www.kernel.org/doc/man-pages/linux-api-ml.html Thanks, Michael On Tue, Nov 20, 2018 at 8:45 PM Waiman Long <longman@xxxxxxxxxx> wrote: > > v4: > - Rebased to the latest for-4.21 branch of cgroup tree. > - Make each controller explicitly opt in to become bypassable by > setting the bypassable cgroup_subsys flag. Currently, only cpu > controller is made bypassable. > - Break out the cgroup_v2.rst documentation update as separate patch. > > 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. > > v3 patch - https://lkml.org/lkml/2017/8/9/604 > > This patchset introduces a new bypass mode to the cgroup v2 core to > give more freedom and flexibility to controllers which choose to become > bypassable the freedom to shape their own unique views of the virtual > cgroup hierarchies that can best suit thier own use cases. > > Because of the inherent performance overhead in enabling cpu controller, > it is made bypassable so that the controller only needs to be enabled > at those cgroups that really need it instead of in every cgroups at a > given layer if at least one of them needs it. > > The cpu controller performance problem is one of the major issues > in migrating from cgroup v1 to v2. > > For example, > > R - A(+) - B(#) - C(+) > \ D(#) > > where "+" means the controller is enabled and "#" means the controller > is bypassed. For this controller's perspective, the cgroups are > equivalent to: > > R - A|B|D - C > > Underneath the root R, cgoups A, B and D are controlled by one set of > knobs and cgroup C is controlled by another set of knobs as a child of > cgroups A|B|C. > > This patchset is layered on top of the "for-4.21" branch of Tejun's > cgroup git tree. > > Patch 1 introduces a new bypass mode that allows a bypassable > controller to be disabled in a cgroup, but to be 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 bypassable 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. > > Patch 4 makes the cpu controller bypassable. > > Patch 5 documents the new bypass mode in cgroup-v2.rst file. > > Waiman Long (5): > cgroup: subtree_control bypass mode for bypassable controllers > cgroup: Allow reenabling of controller in bypass mode > cgroup: Make debug controller report new controller masks > sched/core: Make cpu cgroup controller bypassable > cgroup: Document bypass mode > > Documentation/admin-guide/cgroup-v2.rst | 66 +++++--- > include/linux/cgroup-defs.h | 26 +++- > kernel/cgroup/cgroup.c | 256 +++++++++++++++++++++++++------- > kernel/cgroup/debug.c | 2 + > kernel/sched/core.c | 1 + > 5 files changed, 276 insertions(+), 75 deletions(-) > > -- > 1.8.3.1 > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface", http://blog.man7.org/
