A power-aware scheduling update

Posted Jun 20, 2013 22:41 UTC (Thu) by dlang (guest, #313)
Parent article: A power-aware scheduling update

> Arjan suggests that any discussion that is based on control of CPU frequencies and voltages misses an important point: current processors have a more complex notion of power management, and they vary considerably from one hardware generation to the next. The scheduler is not the right place for all that low-level information; instead, it belongs in low-level, hardware-specific code.

The problem with saying that the scheduler shouldn't care about this is that if it has no idea how fast a core is, or is going to be, how can it possibly attempt to put the right amount of load on it, or charge the process for the time it spent on that core?

According to Arian, the only way to find out how fast a core is running is to measure it, and the speed that a core is running may vary by a factor of 2 without any notice to the OS.

How can any system possibly make reasonable decisions if the hardware is so unpredictable?