lkml.org 
[lkml]   [2021]   [Nov]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] base: arch_topology: Use policy->max to calculate freq_factor
From
Date
Hi,

On 11/17/21 7:49 AM, Rafael J. Wysocki wrote:
> On Wed, Nov 17, 2021 at 11:46 AM Lukasz Luba <lukasz.luba@arm.com> wrote:
>>
>> Hi Rafael,
>>
>> On 11/16/21 7:05 PM, Rafael J. Wysocki wrote:
>>> On Mon, Nov 15, 2021 at 9:10 PM Thara Gopinath
>>> <thara.gopinath@linaro.org> wrote:
>>>>
>>>> cpuinfo.max_freq can reflect boost frequency if enabled during boot. Since
>>>> we don't consider boost frequencies while calculating cpu capacities, use
>>>> policy->max to populate the freq_factor during boot up.
>>>
>>> I'm not sure about this. schedutil uses cpuinfo.max_freq as the max frequency.
>>
>> Agree it's tricky how we treat the boost frequencies and also combine
>> them with thermal pressure.
>> We probably would have consider these design bits:
>> 1. Should thermal pressure include boost frequency?
>
> Well, I guess so.
>
> Running at a boost frequency certainly increases thermal pressure.
>
>> 2. Should max capacity 1024 be a boost frequency so scheduler
>> would see it explicitly?
>
> That's what it is now if cpuinfo.max_freq is a boost frequency.
>
>> - if no, then schedutil could still request boost freq thanks to
>> map_util_perf() where we add 25% to the util and then
>> map_util_freq() would return a boost freq when util was > 1024
>>
>>
>> I can see in schedutil only one place when cpuinfo.max_freq is used:
>> get_next_freq(). If the value stored in there is a boost,
>> then don't we get a higher freq value for the same util?
>
> Yes. we do, which basically is my point.
>
> The schedutil's response is proportional to cpuinfo.max_freq and that
> needs to be taken into account for the results to be consistent.

So IIUC, cpuinfo.max_freq is always supposed to be the highest supported
frequency of a cpu, irrespective of whether boost is enabled or not.
Where as policy->max is the currently available maximum cpu frequency
which can be equal to cpuinfo.max_freq or lower (depending on whether
boost is enabled, whether there is a constraint on policy->max placed by
thermal etc). So in this case isn't it better for schedutil to consider
policy->max instead of cpuinfo.max ? Like you mentioned above same
utilization will relate to different frequencies depending on the
maximum frequency.



>

--
Warm Regards
Thara (She/Her/Hers)

\
 
 \ /
  Last update: 2021-11-17 18:02    [W:0.208 / U:0.388 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site