Power management: Communicating needs and desires

Scheduled: Friday, September 25, 2009 from 10:00 – 10:45am in Salon CD


Implementing power management is the job of the kernel - however, it's userspace's job to let it know what functionality is needed. What interfaces do we need to expose, and how should userspace be making use of them?


Power management is still often thought of as a set of static policies that will be enacted whenever the system becomes idle. However, much of the power savings in a modern system are adaptive and entirely transparent to the user. The aim now is to take this even further. Even greater power savings can be achieved if we can disable certain aspects of hardware functionality. But how can we infer when it’s safe to do so? How can we identify userspace’s needs and make sure that they’re satisfied? How aggressive can we be at entering these lower power states?

This presentation will discuss some of the existing interfaces (such as pm_qos) that exist for userspace to inform the kernel of requirements. It will also discuss what other sources of information already exist and can be tied into power management, along with cases where we lack any infrastructure to communicate desires and hence sacrifice one of either functionality or power. The aim is to identify our current shortcomings and propose ways to allow userspace to communicate its desires to the kernel.


  • Matthew Garrett

    Red Hat


    Matthew Garrett has been working on Linux power management for several years, and recently managed to escape fruit flies in order to focus on it full time. He now works for Red Hat with responsibility for beating on whichever part of the stack is currently responsible for sucking excessive amounts of power. He may fix your laptop if asked sufficiently nicely.

Leave a private comment to organizers about this proposal