cgroup: Add test_cpucg_max_nested() testcase

The cgroup cpu controller selftests have a test_cpucg_max() testcase
that validates the behavior of the cpu.max knob. Let's also add a
testcase that verifies that the behavior works correctly when set on a
nested cgroup.

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup: Add test_cpucg_max() testcase

The cgroup cpu controller test suite has a number of testcases that
validate the expected behavior of the cpu.weight knob, but none for
cpu.max. This testcase fixes that by adding a testcase for cpu.max as well.

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup: Add test_cpucg_nested_weight_underprovisioned() testcase

The cgroup cpu controller test suite currently contains a testcase called
test_cpucg_nested_weight_underprovisioned() which verifies the expected
behavior of cpu.weight when applied to nested cgroups. That first testcase
validated the expected behavior when the processes in the leaf cgroups
overcommitted the system. This patch adds a complementary
test_cpucg_nested_weight_underprovisioned() testcase which validates
behavior when those leaf cgroups undercommit the system.

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup: Adding test_cpucg_nested_weight_overprovisioned() testcase

The cgroup cpu controller tests in
tools/testing/selftests/cgroup/test_cpu.c have some testcases that validate
the expected behavior of setting cpu.weight on cgroups, and then hogging
CPUs. What is still missing from the suite is a testcase that validates
nested cgroups. This patch adds test_cpucg_nested_weight_overprovisioned(),
which validates that a parent's cpu.weight will override its children if
they overcommit a host, and properly protect any sibling groups of that
parent.

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup: Add test_cpucg_weight_underprovisioned() testcase

test_cpu.c includes testcases that validate the cgroup cpu controller.
This patch adds a new testcase called test_cpucg_weight_underprovisioned()
that verifies that processes with different cpu.weight that are all running
on an underprovisioned system, still get roughly the same amount of cpu
time.

Because test_cpucg_weight_underprovisioned() is very similar to
test_cpucg_weight_overprovisioned(), this patch also pulls the common logic
into a separate helper function that is invoked from both testcases, and
which uses function pointers to invoke the unique portions of the
testcases.

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup: Add test_cpucg_weight_overprovisioned() testcase

test_cpu.c includes testcases that validate the cgroup cpu controller.
This patch adds a new testcase called test_cpucg_weight_overprovisioned()
that verifies the expected behavior of creating multiple processes with
different cpu.weight, on a system that is overprovisioned.

So as to avoid code duplication, this patch also updates cpu_hog_func_param
to take a new hog_clock_type enum which informs how time is counted in
hog_cpus_timed() (either process time or wall clock time).

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup: Add test_cpucg_stats() testcase to cgroup cpu selftests

test_cpu.c includes testcases that validate the cgroup cpu controller.
This patch adds a new testcase called test_cpucg_stats() that verifies the
expected behavior of the cpu.stat interface. In doing so, we define a
new hog_cpus_timed() function which takes a cpu_hog_func_param struct
that configures how many CPUs it uses, and how long it runs. Future
patches will also spawn threads that hog CPUs, so this function will
eventually serve those use-cases as well.

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup: Add new test_cpu.c test suite in cgroup selftests

The cgroup selftests suite currently contains tests that validate various
aspects of cgroup, such as validating the expected behavior for memory
controllers, the expected behavior of cgroup.procs, etc. There are no tests
that validate the expected behavior of the cgroup cpu controller.

This patch therefore adds a new test_cpu.c file that will contain cpu
controller testcases. The file currently only contains a single testcase
that validates creating nested cgroups with cgroup.subtree_control
including cpu. Future patches will add more sophisticated testcases that
validate functional aspects of the cpu controller.

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Tejun Heo <tj@kernel.org>