Processor Duty Cycle Alignment with Interrupts
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Solution Overview
Problem
The increasing power requirements and energy consumption of multicore processors pose a significant challenge for energy efficiency, particularly in computing systems where power management techniques have not effectively aligned the activity of multiple computing engines to enter low power states synchronously, leading to delayed interrupt processing and reduced quality of service.
Innovation Solution
A power control unit (PCU) is implemented to synchronize the active and idle states of computing engines based on impending interrupts, dynamically adjusting duty cycles to ensure that interrupts are handled promptly, thereby enabling longer and deeper low power states without performance tradeoffs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If computing engines enter low power states synchronously without considering interrupt timing, then power savings are improved, but interrupt processing latency increases and quality of service deteriorates
Solution Approach 1:
The system performs preliminary action by extending the active state duration before entering low power states, based on predicted interrupt arrival patterns. This proactive adjustment ensures that when interrupts occur, the computing engines are already awake and ready to process them immediately, thus reducing interrupt latency while still maintaining extended low power states for energy savings.
Solution Approach 2:
The duty cycle parameters are made dynamic rather than static. The system continuously monitors interrupt patterns and adjusts the active and idle state durations in real-time. When interrupt activity increases, the active state is extended; when interrupt activity decreases, the system can enter deeper low power states, thus adapting to changing conditions to balance power savings and responsiveness.
2Productivity
If computing engines remain in active state to handle interrupts promptly, then interrupt processing performance is improved, but power consumption increases
Solution Approach 1:
The system implements periodic duty cycling where computing engines alternate between active and low power states in regular cycles. By optimizing the period and duty ratio based on interrupt patterns, the system achieves a balance where engines are active long enough to handle interrupts efficiently but remain in low power states sufficiently to conserve energy, thus achieving periodic operation that satisfies both performance and power constraints.
3Device complexity
If duty cycle parameters are fixed, then system simplicity is maintained, but adaptability to varying interrupt patterns is reduced
Solution Approach 1:
The system implements self-service by automatically monitoring its own interrupt patterns and autonomously adjusting its duty cycle parameters without external intervention. The computing engines or a dedicated power management unit detect interrupt arrivals and dynamically modify active/idle state durations, enabling the system to adapt to varying workloads while maintaining relatively simple control logic that requires no complex external scheduling or configuration.
Data Source
AI summary
In an embodiment, a processor includes a plurality of cores to independently execute instructions, at least one graphics engine to independently execute graphics instructions, and a power controller including a duty cycle logic to set a duty cycle having a cycle time formed of an active time window in which at least some of the plurality of cores are to be active and an idle time window in which the plurality of cores are to be in a low power state. The duty cycle logic may adjust a duration of at least one of an active time window and an inactive time window based on interrupt information to accommodate an impending interrupt within the active time window. Other embodiments are described and claimed.