Question on CPU Frequency subsystem

Question on CPU Frequency subsystem

[Yogesh Kumar]

Hi,

I had a question on CPU Frequency subsystem. As there are multiple
governors which can be set on different CPU cores. If we have 4 cores
lying under the one power domain and voltage rail and suppose governor
setting is:

cpu0: performance
cpu1: on demand
cpu2: on demand
cpu3: performance

Since All cores are lying under same power rails, as we set the cpu0
to performance governor which will set the cpu0 and cpu3 to maximum
frequency and hence sustainable voltage for that frequency but cpu1
and cpu2 are using on demand governor, suppose the load is low on cpu1
and cpu2 cores, therefore on demand governor will try to set the low
frequency and voltage based on the load. Since cpu0 is at high
frequency and cpu1 is at low frequency, which part of cpufreq system
will restrict the voltage to stay high as voltage rail is shared and
one cpu is running at low frequency and another at high frequency?

Regards
Yogesh

Re: Question on CPU Frequency subsystem

[Yogesh Kumar]

 Hi,

 I had a question on CPU Frequency subsystem. As there are multiple
 governors which can be set on different CPU cores. If we have 4 cores
 lying under the one power domain and voltage rail and suppose governor
 setting is:

 cpu0: performance
 cpu1: on demand
 cpu2: on demand
 cpu3: performance

 Since All cores are lying under same power rails, as we set the cpu0
 to performance governor which will set the cpu0 and cpu3 to maximum
 frequency and hence sustainable voltage for that frequency but cpu1
 and cpu2 are using on demand governor, suppose the load is low on cpu1
 and cpu2 cores, therefore on demand governor will try to set the low
 frequency and voltage based on the load. Since cpu0 is at high
 frequency and cpu1 is at low frequency, which part of cpufreq system
 will restrict the voltage to stay high as voltage rail is shared and
 one cpu is running at low frequency and another at high frequency?

 Regards
 Yogesh