Add tests for memory.oom.group for the following cases:
- Killing all processes in a leaf cgroup, but leaving the
  parent untouched
- Killing all processes in a parent and leaf cgroup
- Keeping processes marked by OOM_SCORE_ADJ_MIN alive when considered
  for being killed by the group oom killer.
Signed-off-by: NJay Kamat <jgkamat@fb.com>
Acked-by: NRoman Gushchin <guro@fb.com>
Signed-off-by: NShuah Khan (Samsung OSG) <shuah@kernel.org>

The test verifies that when there is active TCP connection, the
memory.stat.sock and memory.current values are close.
Signed-off-by: NMike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: NRoman Gushchin <guro@fb.com>
Signed-off-by: NShuah Khan (Samsung OSG) <shuah@kernel.org>

The new test verifies that memory.swap.max and memory.swap.current behave
as expected for simple allocation scenarios
Signed-off-by: NMike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: NTejun Heo <tj@kernel.org>
Acked-by: NRoman Gushchin <guro@fb.com>
Signed-off-by: NShuah Khan (Samsung OSG) <shuah@kernel.org>

Cgroups are used for controlling the physical resource distribution
(memory, CPU, io, etc) and often are used as basic building blocks
for large distributed computing systems. Even small differences
in the actual behavior may lead to significant incidents.

The codebase is under the active development, which will unlikely
stop at any time soon. Also it's scattered over different kernel
subsystems, which makes regressions more probable.

Given that, the lack of any tests is crying.

This patch implements some basic tests for the memory controller,
as well as a minimal required framework. It doesn't pretend for a
very good coverage, but pretends to be a starting point.

Hopefully, any following significant changes will include corresponding
tests.

Tests for CPU and io controllers, as well as cgroup core
are next in the todo list.
Signed-off-by: NRoman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: kernel-team@fb.com
Cc: linux-kselftest@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NShuah Khan (Samsung OSG) <shuah@kernel.org>