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[Obleak <800991@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

I can across an interesting issue with HD playback which no doubt is due
to the hardware and the way I use the machine.

The cpu frequency scaling applied by default is very conservative, only scaling up the CPU when usage reaches 95%
The CPU usage whilst playing HD content was sitting at ~60% with the CPU running at it's lowest speed (1GHz)
With a few recordings going on the backend this starts creeping up to 80%

Occasionally another process would spawn and the CPU would find itself
briefly hitting 100% - which caused dropped frames on playback - It's
only brief as the cpu polling sees the increased usage and increases the
frequency (so we are only talking <100ms of 100%)

What I've found is by reducing the  "Up_threshold" in the ondemand
profile to 60%, The CPU scales up before reaching 100% now - so in
affect I've given it some headroom to cope with other tasks and this has
been enough to eliminate the occasional dropped frame.

I've done this by adding the following to the /etc/init.d/ondemand startup script
echo -n 60 > /sys/devices/system/cpu/cpu0/cpufreq/ondemand/up_threshold


So not really a bug but more of an optimisation report - perhaps there is some customisation of the CPU power/utilisation needed with Mythtv? - delivery of content is paramount IMHO and the frontend should ensure it has the resources it needs to deliver content.

** Affects: mythbuntu
     Importance: Undecided
         Status: New


** Tags: cpufreq

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https://bugs.launchpad.net/bugs/800991

Title:
  Default "ondemand" CPU frequency management can cause 100% CPU

Status in Mythbuntu, Ubuntu derivative focused upon MythTV:
  New

Bug description:
  I can across an interesting issue with HD playback which no doubt is
  due to the hardware and the way I use the machine.

  The cpu frequency scaling applied by default is very conservative, only scaling up the CPU when usage reaches 95%
  The CPU usage whilst playing HD content was sitting at ~60% with the CPU running at it's lowest speed (1GHz)
  With a few recordings going on the backend this starts creeping up to 80%

  Occasionally another process would spawn and the CPU would find itself
  briefly hitting 100% - which caused dropped frames on playback - It's
  only brief as the cpu polling sees the increased usage and increases
  the frequency (so we are only talking <100ms of 100%)

  What I've found is by reducing the  "Up_threshold" in the ondemand
  profile to 60%, The CPU scales up before reaching 100% now - so in
  affect I've given it some headroom to cope with other tasks and this
  has been enough to eliminate the occasional dropped frame.

  I've done this by adding the following to the /etc/init.d/ondemand startup script
  echo -n 60 > /sys/devices/system/cpu/cpu0/cpufreq/ondemand/up_threshold

  
  So not really a bug but more of an optimisation report - perhaps there is some customisation of the CPU power/utilisation needed with Mythtv? - delivery of content is paramount IMHO and the frontend should ensure it has the resources it needs to deliver content.

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