SoT screen on time - why it is *not* a universal measurement for ROM / kernel battery management

SoT_is__not__universal.txt

Android SoT is not a universal measurement of a ROM's or a kernel's battery management.

It strongly depends on way too many factors, like:
- display brightness
- mobile connectivity (signal strength / signal to noise ratio, network type, scanning / looking for better coverage..)
- wifi connectivity (signal strength / signal to noise ratio, network type,
  number of neighboring devices (RF field busyness, etc..)
- frequency settings of SoC (CPU & GPU), governor behavor & "boosting" settings
  (too much/too high? Possibly too much drainage..
   too less/too low? Possibly battery friendly but leading to too laggy UI behavior..)
- thermal throttling (reducing RIL capabilities will cause lower network speeds / reductions / restrictions
  and thus the same amount of data traffic needs more time
  and since the user is waiting but the UI & display is active the drainage will be higher)
- background apps and their activities (syncing data, userspace wakelocks, alarms in apps triggering activities
  (refreshing data, etc..), lots of notifications via GMS, network location provider (NLP) wakelocks..)
- actual app usage pattern: 2D gaming // browsing the web // instant massaging // watching Youtube
  (strongly depending on the video quality!) // 3D gaming are resulting / needing _way different_ CPU & GPU load
  thus the same amount of "screen on time" made by different kind of activities are producing _way different_ drainage
  and I hope this is trivial now for everyone ;)

If you want to measure a ROM's and/or kernel's battery management
then create / know your baseline of usage and then you can compare the ROM's and/or kernels, like:
- open the same video player and play the same video on different ROMs and/or kernels
- disable almost everything and leave the phone totally idle for hours and check the battery drainage
- be creative and create your own usage baseline..
..and then you will know how good is the ROM and/or kernel in terms of battery management.

Please, whenever you publish a SoT value just let people know your usage pattern as well.
Without that info the SoT value itself is completely useless. I know this needs a lot of work..
But many people are complaining out there and have no idea what's the background..


PS - just an advise: if you think about it..
finishing a task in less time and going back to idle is much better
than finish it in more time and go back to idle..
It will results a snappier UI and more energy efficient - in my opinion.
Check the voltage/frequency table of your SoC in the kernel source
and try to find the most efficient frequencies,
use interactive CPU governor and set an appropriate freq. for hi-speed,
increase if necessary but go back to idle shortly when load reduces.
So set your CPU/GPU governors accordingly.

Have fun!