Context Snooper and Cache for Fast CPU Suspend Resume
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Solution Overview
Problem
Current systems face challenges in power conservation due to the time-consuming process of transferring control between main and low power CPUs, leading to higher power consumption and reduced responsiveness, as frequent powering down and restoration of the main CPU can impact user experience.
Innovation Solution
A system and method utilizing a context snooper and context cache to monitor and store context changes, allowing the main CPU to be powered down more frequently by accelerating suspend and resume operations, with context information being saved and restored efficiently between a context cache and memory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the main CPU is powered down frequently to conserve power, then power consumption is reduced, but the transfer time between main and low power CPU increases
Solution Approach 1:
The context snooper continuously monitors and captures context changes before the CPU needs to be powered down, pre-loading context information into the context cache. This preliminary action ensures that when suspend/resume operations are needed, the context is already prepared and available, eliminating delays during the actual power transition.
Solution Approach 2:
The context snooper acts as an intermediary component that sits between the CPU context area and the cache/memory system. It intercepts and monitors context changes, selectively capturing only relevant context information and storing it in the context cache, thereby mediating the data flow and reducing the burden on the main CPU during suspend/resume operations.
2Use of energy by moving object
If the main CPU is powered down more frequently, then power savings increase, but application responsiveness deteriorates
Solution Approach 1:
The system creates a copy of the CPU context information and stores it in the context cache before power down. This copy mechanism allows the low power CPU to quickly restore execution state without requiring the main CPU to be fully powered on first, thereby maintaining application responsiveness while enabling frequent power down cycles for savings.
Solution Approach 2:
By continuously monitoring and pre-capturing context changes in the context cache, the system prepares all necessary context information before the suspend operation begins. This preliminary preparation ensures that resume operations can occur rapidly, maintaining user-perceived responsiveness even with frequent power down events.
3Speed
If context changes are monitored and saved frequently, then resume speed is improved, but device complexity increases
Solution Approach 1:
The context snooper implements selective monitoring, capturing only specific context changes that are relevant to CPU state restoration rather than all possible changes. This localized approach to context capture focuses resources on critical information, improving resume speed without proportionally increasing the complexity of the monitoring mechanism.
Solution Approach 2:
The context snooper serves as an intermediary layer that simplifies the complexity by abstracting the monitoring and capture logic away from both the main CPU and the cache system. It provides a standardized interface for context capture, reducing the overall system complexity despite the added functionality for continuous monitoring and selective context saving.
Data Source
AI summary
An apparatus and method are disclosed for improving power savings by accelerating suspend and resume operations. The apparatus having a main integrated circuit, the integrated circuit having a context area, a context snooper, and a context cache, the context area configured to store context change information, the context snooper configured to monitor the context change information, and the context cache configured to store at least a portion of the context change information being monitored by the context snooper; and a memory, the memory configured to receive the at least a portion of the context change information from the context cache upon a suspend process signal to the main integrated circuit, to retain contents during the main integrated circuit suspend, and restore the at least a portion of the context change information to the context cache and/or the context area upon a resume process signal to the main integrated circuit.