Messages in this thread | | | Date | Fri, 21 May 2010 12:43:09 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 2/2] cpuidle: Add a repeating pattern detector to the menu governor |
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On Wed, 19 May 2010 12:51:50 -0700 Frank Rowand <frank.rowand@am.sony.com> wrote:
> Aplogies if this is a duplicate, my outgoing email seems to have not > been working. > > On 05/09/10 16:04, Arjan van de Ven wrote: > > > +/* > > + * Try detecting repeating patterns by keeping track of the last 8 > > + * intervals, and checking if the standard deviation of that set > > + * of points is below a threshold. If it is... then use the > > + * average of these 8 points as the estimated value. > > + */ > > +static void detect_repeating_patterns(struct menu_device *data) > > +{ > > + int i; > > + uint64_t avg = 0; > > + uint64_t stddev = 0; /* contains the square of the std deviation */ > > + > > + /* first calculate average and standard deviation of the past */ > > + for (i = 0; i < INTERVALS; i++) > > + avg += data->intervals[i]; > > + > > + /* if the avg is beyond the known next tick, it's worthless */ > > + if (avg > data->expected_us) > > + return; > > + > > Should the following division by INTERVALS be moved up 6 lines to before > "if (avg > data->expected_us)"?
Quite possibly.
> > + avg = avg / INTERVALS; > > + for (i = 0; i < INTERVALS; i++) > > + stddev += (data->intervals[i] - avg) * > > + (data->intervals[i] - avg); > > + > > + stddev = stddev / INTERVALS; > > + > > + /* > > + * now.. if stddev is small.. then assume we have a > > + * repeating pattern and predict we keep doing this. > > + */ > > + > > + if (avg && stddev < STDDEV_THRESH) > > + data->predicted_us = avg; > > +}
wakey wakey, Arjan.
Also, expected_us is 32-bit and predicted_us is 64-bit. Was that rational?
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