On Wed, Sep 10, 2014 at 8:59 PM, <Valdis.Kletnieks@vt.edu> wrote:
On Wed, 10 Sep 2014 20:26:48 +0300, Ran Shalit said:
What is usually the criterion for PM (power management) suspending that application shall use ? Is it according to minimum threshold for cpu load (as indication for no process) ?
That will be highly application dependent. Something that checks your email in the background may not care at all, as long as it gets network access every 5 minutes or so, and the entire system can power down for 4 minutes and 58 seconds as far as it cares. If it's doing media streaming, it may insist on having at least one CPU burst per screen refresh, and the CPU can go to sleep for the rest of the 1/30th of a second.
How usually it is performed, i.e. is it some periodic process, which wakes up periodically to check criterion for cpu load ? If so, isn't it problematic in PM terms, becuase it mean that the system is resumed periodically (as a result of the the periodic timer's interrupt), and all devices are resumed ?
No, it can be done on a per-device basis.
'powertop' is a possibly useful tool for playing with this stuff that will let you look at power management on the fly.
As far as I understand, suspend/respond PM is not per device, but for all system, and wakeup source will resume again the whole system. I think you mean runtime suspend/resume in the answer.