On Mon, 2016-02-22 at 13:54 +0100, Rafael J. Wysocki wrote:
On Mon, Feb 22, 2016 at 12:27 PM, Viresh Kumar <viresh.kumar@linaro.o rg> wrote:
Hi,
I am not really an intel-pstate driver guy, just wrote the patch based on software-review of the stuff :)
On 22-02-16, 10:17, Chen, Yu C wrote:
IIRC, 1.HWP is hardwarely per-package, CPUs inside one package have one shared HWP. 2.Currently all the CPUs share the same HWP settings according to intel_pstate design. 3. The policy is per-cpu in intel_pstate driver.(policy->cpus only contains one cpu)
So with this patch applied, it is likely CPUs may have different HWP settings?
I think the hardware should be able to cope with that, and should be selecting the frequency based on the highest frequency requested for the same package. Otherwise, why should there be an option to supply per-cpu settings ?
Right.
I can easily imagine a use case in which someone may want to have different ranges for different CPUs.
For example: CPU 0 belongs to package A with policy 0, and CPU 1 belongs to package B with policy 1, If you change the policy 0 from powersave to performance, then only CPU0 will update its min/max freq in HWP, however we should also update CPU 2's min/max in HWP settings? Plz correct me if I'm wrong..
I will let the official intel-pstate guys reply to that.
My opinion is to do what your patch does until that proves to be a problem in practice.
I agree. If someone just changes policy in one CPU, even with current code (before this patch) we have issue, we will change the limits in processor for all online CPUs, but cpufreq core policy will be update for current CPU only. I suggest users to use cpupower like utility if someone want to change policy, which will change for all.
Thanks, Srinivas
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