Processor Core Power Event Tracing for Mobile Responsiveness
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Solution Overview
Problem
Modern processors face challenges in managing power efficiently to extend battery life in mobile computing devices without negatively impacting user experience, as aggressive power-saving decisions can lead to perceivable delays and responsiveness issues.
Innovation Solution
Implementing processor core power event tracing with dedicated trace functionality that generates specific trace packets to provide detailed insights into power management events and decisions, allowing for improved debugging and optimization of power management algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If aggressive power-saving decisions are implemented to extend battery life, then energy consumption is reduced, but user experience deteriorates due to perceivable delays and responsiveness issues
Solution Approach 1:
The system segments power management by creating separate trace pipelines for different power events (entry, exit, suspend, resume) and different processor components (cores, uncore). This segmentation allows selective tracing of only the most critical power events, reducing overall tracing overhead while maintaining visibility into key power management activities that impact responsiveness.
Solution Approach 2:
The system implements partial action by providing an optional trace enablement mechanism where power event tracing can be selectively activated. When enabled, detailed tracing occurs; when disabled, no tracing overhead is incurred. This allows the system to obtain detailed power management insights only when needed for debugging or optimization, rather than continuously, thus minimizing the impact on power consumption and system performance.
2Measurement precision
If detailed power management tracing is implemented, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system merges power event tracing functionality with the existing performance monitoring unit (PMU) infrastructure. By integrating power event tracing into the existing PMU framework, the patent leverages already-present hardware resources for event detection and counting, thereby achieving detailed power management measurements without adding separate complex tracing hardware.
Solution Approach 2:
The trace packet format is designed to be universal and multi-functional, capable of carrying information about various types of power events (core entry/exit, uncore suspend/resume, etc.) through a standardized structure. This universal format eliminates the need for separate specialized tracing mechanisms for each power event type, reducing overall system complexity while maintaining comprehensive measurement precision.
3Loss of information
If power management events are traced with high precision, then information completeness is improved, but energy consumption increases
Solution Approach 1:
The system extracts only the essential power management event information into compact trace packets, rather than capturing all possible details. By selectively extracting key event data (event type, timestamp, core ID, etc.) into a streamlined format, the system achieves sufficient information completeness for power management analysis while minimizing the data volume that requires processing and transmission, thus reducing tracing energy overhead.
Data Source
AI summary
A processor includes a trace unit to monitor activity by the processor and generate trace packets indicative of the activity by the processor. The trace packets may include four additional packets for processor event tracing including: a dormant state request packet, a code execution stop packet, a dormant state entry packet, and a dormant state exit packet.