Copyright by William Lloyd Bircher 2010 - The Laboratory for ...

Chapter 5 Modeling System-Level Power
using Trickle-Down Events
This chapter presents system-level power models based on performance counter events
within the processor. The first section defines the concept and intuition behind trickle-
down performance events. The second section describes the server power model. The
last section describes the laptop power model.
5.1 Processor Events Propagate to Rest of System
Trickle-down power modeling provides an accurate representation of complete-system
power consumption using a simple methodology. The approach relies on the broad
visibility of system-level events to the processor. This allows accurate, performance
counter based models to be created using only events local to the processor. These local
events can be measured using ubiquitous performance counters found in all modern
microprocessors. Local events are preferred since power models can be built using a
single interface. There is no need to create interfaces to multiple devices and subsystems
which have inconsistent or incomplete performance counter APIs (Application
Programming Interface). It is particularly common at the system level since components
are often designed by multiple vendors. Trickle-down modeling also addresses hardware
costs in systems implementing direct measurement. Rather than providing sensors and
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