Processor Power State Demotion Logic
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Solution Overview
Problem
Deep low power states in computer processors introduce performance degradation and energy inefficiencies due to entry and exit latency, loss of architectural information, and energy costs associated with saving and restoring state, leading to higher energy consumption from frequent power state transitions.
Innovation Solution
Implementing power state demotion logic that automatically transitions from deeper power states to shallower states based on core and processor-level metrics, such as average break events, to reduce energy consumption and improve performance by selecting optimal power states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the processor enters deep low power states, then power consumption is reduced, but performance degrades due to entry and exit latency
Solution Approach 1:
The system dynamically adjusts power state transitions based on workload characteristics and performance requirements. The demotion logic monitors break events and actively prevents transitions to deep power states when performance would be degraded, creating a dynamic balance between power savings and performance maintenance
Solution Approach 2:
The processor implements feedback mechanisms by monitoring break events and using this information to control power state transitions. The demotion logic receives feedback about workload changes and adjusts power state selection accordingly, preventing transitions that would cause performance degradation while allowing transitions that provide energy savings
2Loss of energy
If the processor enters deep low power states, then power consumption is reduced, but energy is lost due to save and restore operations
Solution Approach 1:
The system performs preliminary assessment of workload characteristics before allowing transitions to deep power states. The demotion logic evaluates break event patterns in advance to determine whether a transition would be beneficial, preventing transitions that would result in net energy loss from save and restore operations
3Loss of energy
If the processor enters deep low power states, then power consumption is reduced, but architectural information is lost requiring restoration
Solution Approach 1:
The processor implements feedback mechanisms by monitoring break events and using this information to control power state transitions. The demotion logic receives feedback about workload changes and adjusts power state selection accordingly, preventing transitions that would cause performance degradation while allowing transitions that provide energy savings
Data Source
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AI summary
In an embodiment, a processor for demotion includes a plurality of cores to execute instructions and a demotion control circuit. The demotion control circuit is to: for each core of the plurality of cores, determine an average count of power state break events in the core; determine a sum of the average counts of the plurality of cores; determine whether the average count of a first core exceeds a first demotion threshold; determine whether the sum of the average counts of the plurality of cores exceeds a second demotion threshold; and in response to a determination that the average count of the first core exceeds the first demotion threshold and the sum of the average counts exceeds the second demotion threshold, perform a power state demotion of the first core. Other embodiments are described and claimed.