On Thu, Dec 19, 2019 at 03:07:15PM -0500, Johannes Weiner wrote:

Changes since v1:
- improved Changelogs based on the discussion with Roman. Thanks!
- fix div0 when recursive & fixed protection is combined
- fix an unused compiler warning

The current memory.low (and memory.min) semantics require protection
to be assigned to a cgroup in an untinterrupted chain from the
top-level cgroup all the way to the leaf.

In practice, we want to protect entire cgroup subtrees from each other
(system management software vs. workload), but we would like the VM to
balance memory optimally *within* each subtree, without having to make
explicit weight allocations among individual components. The current
semantics make that impossible.

Acked-by: Tejun Heo <tj@kernel.org>

The original behavior turned out to be a significant source of
mistakes and use cases which would require older behavior just weren't
there.

Thanks.

-- 
tejun