Power Management: Policy? We don’t need no stinking policy!+

Yep. Here is another blog series from yours truly. Unfortunately, it will delay my long awaited – at least by me – discussion on measuring power.

Here is a rough outline for the blogs:

1. Introduction and motivation
2. Power management infrastructure
3. Types of power management policies
4. Policies implemented on the Intel® Xeon Phi™ coprocessor

I am only writing about processor (including the Intel Xeon Phi coprocessor) power management, meaning P, C and T states. D (device) and S (standby & hibernate) states are a different topic –though no less important in more general purpose systems. See the APCI specification in the reference below [LIST0].

This series is about power management policy. This policy defines how a system, e.g. the OS, implements power management. Hopefully, this is going to be a relatively short series. The truth is that I can never tell until I have written at least half of it.

The primary reason I am writing this series is because I made a minor error about the power management policy implemented by the Intel® Manycore Platform Software Stack (MPSS). This in turn pointed out that I had not yet written about the difference between power management policy and power management implementation. This is not simply an abstract discussion as the coprocessor has two policies available to it. I will discuss both later.

The secondary reason is that it completes the power management picture as policies are not monolithic and have changed over the years. The policy implemented by a system depends upon both the capabilities of the hardware (e.g. support of C-states) and the needs of the environment (e.g. HPC versus social media).

The next blog in this series will look at power management from a system’s perspective.

COMING NEXT: WHAT EXACTLY IS A POWER MANAGEMENT POLICY?

⁺Paraphrasing a famous quote from John Huston’s movie, “The Treasure of Sierra Madre.”

REFERENCES

[LIST0] For a list of previous blogs in this series, and well as other related blogs on power and power management, see the article at http://software.intel.com/en-us/articles/list-of-useful-power-and-power-management-articles-blogs-and-references.