Hello,
On Thu, Sep 26, 2013 at 10:32 PM, Viresh Kumar <[email protected]> wrote:
>
> On 26-Sep-2013 10:03 PM, "Ryan" <[email protected]> wrote:
>>
>> Can you explain a little bit, I read somewhere that it is due to ping
>> pong. but i was not able to visualize that part.
>> How it could happen.
>
> Suppose load is changing between 90 and 99, then due to down diff we will
> keep running at max freq.. otherwise continuos switching will hqppen..
Let me understand how the downscaling works in the older sources.
So, you mean that -
1) Upthreshold = 95%
down dif = 5%
so, upthreshold - down diff = 90%
if load is 85% ; cpu downscaling takes place
if load is 75% ; cpu downscaling takes place
and so on.
So everytime for sampling rate period - work queue checks and finds
the load and downscaling takes place if less than 90%.
What i did not understand is how down diff will make the cpu remain in
the same range for a longer period.
Am i missing something. could you please give a detailed answer as i
struggling to understand this.
Thanks for your time.
/ryan
>
>> also when you say that
>>
>> "Latest ondemand gov keeps freq proportional to load all the time..
>> and switches to max freq directly if load is over 95"
>> you mean to say there is no down differential part of 5%?
>
> Not that.. in earlier code we will not inc freq while load is less than up
> thresh.. but now if load is less than up thresh but greater than last load,
> we will inc freq by some amount.. and so we end up using middle freqs more
> now..
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