touch-packages team mailing list archive

[Daniel van Vugt <daniel.van.vugt@xxxxxxxxxxxxx>]

Three things I have found that solve the stuttering from premature CPU
scaling on Android:

  * Don't use nesting. Having a single server architecture seems to keep it smooth.
  * Don't use double buffering (bug 1240909). Staying busy pre-rendering that third buffer keeps clocks higher and smoother.
  * Just wastefully spin a CPU core. Annoyingly, wasting power makes graphics visibly smoother.

Hopefully we can find more options.

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Touch seeded packages, which is subscribed to mir in Ubuntu.
https://bugs.launchpad.net/bugs/1488386

Title:
  [performance] Double buffering is only smooth while you're touching it

Status in Mir:
  New
Status in QtMir:
  New
Status in mir package in Ubuntu:
  New
Status in qtmir package in Ubuntu:
  New

Bug description:
  On some devices (mako at least) it's possible to force double
  buffering and it will often keep up:

     restart unity8 QML_NO_TOUCH_COMPRESSION=1 MIR_SERVER_NBUFFERS=2

  Curiously however it only keeps up smoothly (eg. during a dash scroll)
  while you're touching the screen. If you lift off or fling the dash
  then it immediately stutters, quite badly.

  So the issue is not that the device can't keep up with double buffering. It seems more like we're not keeping the kernel sufficiently awake and it's clocking down prematurely, as soon as we're not touching it. Certainly adjusting the variables in:
     /sys/devices/system/cpu/cpu0/cpufreq
  it is possible to raise the performance and minimum frequency to make double buffering smooth.

  The challenge of this bug is to find a way in Mir/QtMir to keep the
  kernel more awake so it doesn't clock down when we need smooth
  animations and we're not touching the screen.

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