On 08.07.2025 06:02, Penny, Zheng wrote:
>> -----Original Message-----
>> From: Jan Beulich <jbeul...@suse.com>
>> Sent: Tuesday, June 17, 2025 6:38 PM
>>
>> On 27.05.2025 10:48, Penny Zheng wrote:
>>> --- a/tools/misc/xenpm.c
>>> +++ b/tools/misc/xenpm.c
>>> +
>>> +    case XEN_SYSCTL_CPPC_SET_PRESET_BALANCE:
>>> +        if ( set_cppc->set_params & XEN_SYSCTL_CPPC_SET_DESIRED )
>>> +            return -EINVAL;
>>> +        policy->policy = CPUFREQ_POLICY_BALANCE;
>>> +        min_perf = data->caps.lowest_perf;
>>> +        max_perf = data->caps.highest_perf;
>>> +        epp = CPPC_ENERGY_PERF_BALANCE;
>>> +        break;
>>
>> Isn't this more line "ondemand"? To me, "balance" would mean tying perf to 
>> at least
>> close around the middle of lowest and highest.
> 
> The "balance" word comes from the epp value, it is 127, which is the middle 
> value
> In actual hardware algorithm, the value of Energy Performance Preference 
> register(EPP) will be translated to frequency setting,
> And it sets the minimum active frequency.
>  An EPP of zero sets the min active frequency to Fmax, while an EPP of 255 
> sets the min active frequency to Fmin (~IdleFreq).  It is linear scaling, so 
> epp of 127 is calculated to the middle of Fmax and Fmin.
> And Fmax corresponds to the highest perf, and Fmin corresponds to the 
> non-linear lowest perf

I'm fine with the EPP value picked here. My question - as to the min_perf and
max_perf values that you set - remains, though.

Jan

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