On Tue, Jun 10, 2014 at 12:16:22PM +0200, Peter Zijlstra wrote: > What other target would you optimize for? The purpose here is to build > an energy aware scheduler, one that schedules tasks so that the total > amount of energy, for the given amount of work, is minimal. > > So we can't measure in Watt, since if we forced the CPU into the lowest > P-state (or even C-state for that matter) work would simply not > complete. So we need a complete energy term. > > Now. IPC is instructions/cycle, Watt is Joule/second, so IPC/Watt is > > instructions second > ------------ * ------ ~ instructions / joule > cycle joule > > Seeing how both cycles and seconds are time units. > > So for any given amount of instructions, the work needs to be done, we > want the minimal amount of energy consumed, and IPC/Watt is the natural > metric to measure this over an entire workload.
Ok, I understand. Whether we take IPC/watt as an input metric in scheduler or as a goal for scheduler, we definitely need to try both. Thanks, Peter. Yuyang -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
