Comment 21 for bug 1917813

Created attachment 294685
a set of tools for an automated test

At this point, I have provided 3 different methods that reveal the same HWP issue. Herein, tools are provided to perform an automated quick test to answer the question "does my processor have this HWP issue?"

The motivation for this automation is to make it easier to test other HWP capable Intel processors. Until now the other methods for manifesting the issue have required "tweeking", and have probabilities of occurrence even lower than 0.01%, requiring unbearably long testing times (many hours) in order to acquire enough data to be statistically valid. Typically, this test provides PASS/FAIL results in about 5 minutes.

The test changes idle state enabled/disabled status, requiring root rights to do so. The scale for the fixed workpacket periodic workflow is both arbitrary and different between processors. The test runs in two steps: The first finds the operating point for the test (i.e. it does the "tweeking" automatically); The second does the actual tests one without idle state 2 and one with only idle state 2 (recall that the issue is linked with the use of idle state 2). Forcing idle state 2 greatly increases the probability of the issue occurring. While this test has been created specifically for the intel_pstate CPU frequency scaling driver with HWP enabled and the powersave governor, it doesn't check. Therefore one way to test the test is to try it with HWP disabled.

Note: the subject test computer must be able to run one CPU at 100% without needing to throttle (power or thermal or any other reason), including with only idle state 2 enabled.

Results so far: 3 of 3 processors FAIL; i5-9600k; i5-6200U; i7-10610U.

use this command:

./job-control-periodic 347 6 6 900 10

Legend:
347 hertz work/sleep frequency
6 seconds per iteration run.
6 seconds per test run.
try for approximately 900 uSec average sleep time.
10 test loops at that 6 seconds per test.

the test will take about 5 minutes.