Microarchitectural Scratchpads for Fast Program State Restoration
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Solution Overview
Problem
Modern processors experience inefficiencies in pattern recognition during high context switch rates due to insufficient warm-up of microarchitectural registers, leading to repeated pattern recognition and increased latency.
Innovation Solution
Implementing a microarchitectural scratchpad to store program state data, including the state of microarchitectural registers, allowing for immediate restoration of program state and register values during context switches, thereby reducing the need for a warm-up period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the processor frequently performs context switches between different programs, then the processor can handle multiple programs efficiently, but the microarchitectural registers are insufficiently warmed up and pattern recognition abilities are defeated
Solution Approach 1:
The patent applies preliminary action by storing the microarchitectural register state data in a buffer before context switching occurs. When a program is terminated, its register state is captured and stored in the buffer, so that when the program is restored, the register state is already prepared and can be immediately restored without requiring warm-up period. This resolves the contradiction by preparing the pattern recognition state in advance, allowing frequent context switches without losing pattern recognition accuracy.
2Loss of time
If the processor restores program state data from the buffer during context switching, then the program execution can be resumed quickly, but the microarchitectural register states are not restored and pattern recognition is repeated
Solution Approach 1:
The patent merges the program state data restoration with the microarchitectural register state restoration into a single unified process. The buffer stores both the program counter state and the microarchitectural register states together. When restoring a program, both the program state and the register states are restored simultaneously in one operation, rather than separately. This resolves the contradiction by ensuring that pattern recognition continuity is maintained while achieving quick program restoration.
3Reliability
If the buffer size is increased to store more program state data including microarchitectural register states, then the program restoration completeness is improved, but the buffer memory usage increases
Solution Approach 1:
The patent applies local quality by selectively storing only the necessary microarchitectural register states in the buffer, rather than storing all possible register states or using a uniformly large buffer. The system identifies and stores only the specific register states that are relevant for pattern recognition and program restoration, such as branch predictor states and hardware prefetcher states. This resolves the contradiction by achieving complete program state restoration while minimizing buffer memory usage through targeted storage of critical state data.
Data Source
AI summary
Aspects of the disclosed technology include techniques and mechanisms for restoring program states using microarchitectural scratchpads. A processor is configured to store, in a buffer, program state data which indicates a current state of microarchitectural registers therein during execution of a current program. Based on receiving a command to terminate execution of the current program and restore execution of a different program, the processor retrieves, from the buffer, the program state data associated with the program to be executed and restores the retrieved data.