Cache Memory Power Gating with Prefetch Prediction
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Solution Overview
Problem
In computer systems, the power gating technique to reduce power consumption by stopping power to cache memory during idle states results in unnecessary consumption of power for prefetched data, as the data must be re-read when needed.
Innovation Solution
A control system with a detecting unit to determine if the processing device is idle, a determining unit to decide whether to stop power to the cache memory based on prefetch data usage, and a power supply control unit to manage power supply accordingly, preventing unnecessary power consumption by continuing power supply when prefetched data is likely to be accessed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power supply to cache memory is stopped during idle state to reduce power consumption, then power consumption is reduced, but prefetched data is lost and must be re-read causing unnecessary power consumption
Solution Approach 1:
The patent applies preliminary action by determining whether to stop power supply based on predicted future data access patterns. The system performs prefetch operations in advance and uses prediction algorithms to identify data that will be needed soon, making a decision about power supply before the idle state begins. This allows the system to maintain power supply when prefetched data is likely to be accessed, preventing the loss of information while still enabling power savings when data won't be needed.
2Reliability
If power supply to cache memory is continued during idle state to maintain prefetched data, then data availability is maintained, but power consumption increases
Solution Approach 1:
The patent applies dynamics by making the power supply state dynamic rather than static. The system transitions between powered-on and powered-off states based on real-time predictions of data access patterns. The determination unit dynamically evaluates whether prefetched data is likely to be accessed and adjusts the power supply accordingly, allowing the system to optimize between data availability and power consumption based on actual usage patterns rather than following a fixed policy.
Solution Approach 2:
The patent applies parameter changes by modifying the power supply parameter based on prediction results. The system changes the power supply state (on/off) according to the likelihood of future data access. When the prediction indicates high probability of access, the power supply parameter is set to maintained; when access probability is low, the power supply parameter is changed to stopped, thereby optimizing the balance between data availability and energy consumption.
3Speed
If prefetch operation is performed to read data in advance onto cache memory, then data access speed is improved, but power is consumed unnecessarily when cache memory is powered off
Solution Approach 1:
The patent applies feedback by using the results of data access pattern analysis to control the power supply state. The system performs prefetch operations, then monitors and predicts whether the prefetched data will actually be accessed. Based on this feedback information, the determination unit decides whether to maintain or stop power supply to the cache memory. This closed-loop feedback mechanism ensures that prefetch operations provide actual benefit by maintaining power supply only when the prefetched data is likely to be used, eliminating wasteful power consumption.
Data Source
AI summary
According to an embodiment, a control system includes a processing device; a main storage device to store the data; a cache memory to store part of the data stored; a prefetch unit to predict data highly likely to be accessed and execute prefetch, reading out data in advance onto the cache memory; and a power supply unit. The system further includes: a detecting unit to detect whether the processing device is in an idle state; a determining unit that determines whether to stop the supply of power to the cache memory in accordance with the state of the prefetch when determined as idle state; and a power supply control unit that controls the power supply unit so as to stop the supply of power, or controls the power supply unit so as to continue the supply of power.