The power-aware scheduling mini-summit [LWN.net]

The power-aware scheduling mini-summit

Posted Oct 25, 2013 23:27 UTC (Fri) by jpan9 (subscriber, #37902)
Parent article: The power-aware scheduling mini-summit

One more thing might be worth considering is whether we can synchronize longer idle time slots among all cores. This will give hardware a chance to enter package level C-states, which are getting deeper on the newer processors. The energy saving can be significantly greater than core idle.

If we we can achieve the synchronized idle, spreading work among more cores and enter idle the same time might be better than keeping one core busy such that less package level idle can be achieved. Having information on the power consumption ratio between core and package level will help make the choice.

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The power-aware scheduling mini-summit

Posted Oct 28, 2013 11:10 UTC (Mon) by cmarinas (subscriber, #39468) [Link]

That's an important part of the ARM big.LITTLE architecture - there are two clusters (a.k.a. packages) and one of the approaches is to pack tasks onto a single cluster (usually the little one) to let the other go into deep sleep state. The point the scheduler maintainers have been making is that the scheduler is not aware of these states and power hierarchy, so simple task packing may not be generic enough. Once the scheduler is fully aware of the C-states topology at both CPU and package level, it could make more informed decisions about task placement (it sounds simpler at the high level but rather difficult once you start implementing it).