testcases/kernel/controllers/cpuacct/cpuacct_testplan.txt

The CPU Accounting controller testplan includes a complete set of 
testcases that test the CPU Accounting controller in different scenarios.


TESTCASE DESCRIPTION:
====================

These tests will check if the cpu usage of the child cgroup is 
getting reflected in the parent cgroup.Reports PASS if the cpu 
usage is same for both the cgroups and FAIL if they differ.

In these tests cpu usage of the tasks running in a group is read in 
terms of 3 different stat values.

'cpuacct.usage'  gives the current cpu usage of the task running 
in the group.
'cpuacct.usage_percpu' gives the cpu usage of each cpu.
'cpuacct.stat' gives the user and system cpu usage of the task running 
in the group.

Test01: STAT CHECK TEST
-------------------------------
This test is run by running a task in the child group and reading it's stat 
values and comparing them with the parent group's stat values.

Test02: STAT CHECK TEST
-------------------------------
This test is run by running num_online_cpus number of tasks in 2 child groups, 
adding the stat values from the child groups and comparing them with the 
parent's stat values.

The values reported for user and system time in cpuacct.stat is not very
accurate and they can vary from the actual values by Threshold*num_online_cpus in the
worst case.
Where Threshold T = max(num_online_cpus^2, 32)

In this test case, we allow for a max difference between actual and reported
values to be 2T. If the difference between parent's value and children's value
is greater than 2T, we mark the test as failed.


For any other information please refer to 
Documentation/controllers/cpuacct.txt in kernel documentation.