Re: [PATCH] cpufreq: Fix ondemand governor powersave_bias execution time misuse

Re: [PATCH] cpufreq: Fix ondemand governor powersave_bias execution time misuse

[Arjan van de Ven]

On 11/8/2010 6:45 AM, Youquan Song wrote:
>> On 11/5/2010 11:19 AM, Youquan Song wrote:
>>> Ondemand governor use powersave_bias tunable to do aggressive power save by
>>> decrease CPU average frequency. The average frequency achieve by adjust low and
>>> high frequency's execution time proportion during one sample time interval.
>>>
>>> Current kernel, only the high frequency executes in time proportion, but the low
>>> frequency wrongly execute in one whole sample time interval when powersave_bias
>>> is set.
>>>
>>> The patch fix it by set low frequency execution time to it deserved.
>>>
>>> Signed-off-by: Youquan Song<youquan.song@intel.com>
>>> ---
>>
>> while your patch looks correct, I think the whole feature is wonky and
>> likely ought to be removed...........
> powersave_bias should be a useful feature, which give user an
> opportunity to set the CPU to work at wider average frequency accord to real
>   workload requirement, not just CPU frequency specific at P0,P1,...Pn.
> At the same time, it meets end user power comsumpation requirement in
> some degree.
> Unfortunately, it does not work for a long time.

in all measurements I've done... the intermediate states (between P1 and 
Pn) seem to not be power efficient.....

Re: [PATCH] cpufreq: Fix ondemand governor powersave_bias execution time misuse

[Youquan Song]

> On 11/5/2010 11:19 AM, Youquan Song wrote:
>> Ondemand governor use powersave_bias tunable to do aggressive power save by
>> decrease CPU average frequency. The average frequency achieve by adjust low and
>> high frequency's execution time proportion during one sample time interval.
>>
>> Current kernel, only the high frequency executes in time proportion, but the low
>> frequency wrongly execute in one whole sample time interval when powersave_bias
>> is set.
>>
>> The patch fix it by set low frequency execution time to it deserved.
>>
>> Signed-off-by: Youquan Song<youquan.song@intel.com>
>> ---
>
>
> while your patch looks correct, I think the whole feature is wonky and 
> likely ought to be removed...........

powersave_bias should be a useful feature, which give user an
opportunity to set the CPU to work at wider average frequency accord to real
 workload requirement, not just CPU frequency specific at P0,P1,...Pn.
At the same time, it meets end user power comsumpation requirement in
some degree. 
Unfortunately, it does not work for a long time.

Thanks
-Youquan