On 2019.08.02 02:28 Rafael J. Wysocki wrote:
On Friday, August 2, 2019 11:17:55 AM CEST Rafael J. Wysocki wrote:
On Fri, Aug 2, 2019 at 7:44 AM Viresh Kumar viresh.kumar@linaro.org wrote:
Intel pstate driver exposes min_perf_pct and max_perf_pct sysfs files, which can be used to force a limit on the min/max P state of the driver. Though these files eventually control the min/max frequencies that the CPUs will run at, they don't make a change to policy->min/max values.
That's correct.
When the values of these files are changed (in passive mode of the driver), it leads to calling ->limits() callback of the cpufreq governors, like schedutil. On a call to it the governors shall forcefully update the frequency to come within the limits.
OK, so the problem is that it is a bug to invoke the governor's ->limits() callback without updating policy->min/max, because that's what "limits" mean to the governors.
Fair enough.
AFAICS this can be addressed by adding PM QoS freq limits requests of each CPU to intel_pstate in the passive mode such that changing min_perf_pct or max_perf_pct will cause these requests to be updated.
All governors for the intel_cpufreq (intel_pstate in passive mode) CPU frequency scaling driver are broken with respect to this issue, not just the schedutil governor. My initial escalation had been focused on acpi-cpufreq/schedutil and intel_cpufreq/schedutil, as they were both broken, and both fixed by my initially submitted reversion. What can I say, I missed that other intel_cpufreq governors were also involved.
I tested all of them: conservative ondemand userspace powersave performance schedutil Note that no other governor uses resolve_freq().
... Doug