Processor Power Gating Using Cache Dirtiness Metrics
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Solution Overview
Problem
Power gating in processor systems consumes significant system resources and incurs performance costs due to cache flushing and idle time management, leading to inefficient energy conservation and potential delays when transitioning between power states.
Innovation Solution
Implementing a performance policy manager that selectively power gates components based on cache dirtiness and predicted idle time durations, using measures such as dirty cache line counts and idle state duration predictors to optimize power management decisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power gating is implemented to reduce standby and leakage power consumption, then energy efficiency is improved, but system resources are consumed due to cache flushing and performance overhead is incurred
Solution Approach 1:
The patent changes the decision parameter for power gating from a simple idle time threshold to a composite parameter that includes cache dirtiness metrics. By monitoring the number of dirty cache lines and using this as a key parameter in the power gating decision, the system optimizes the trade-off between power savings and the cost of cache flushing. The power gating decision is made by comparing predicted idle time against a threshold that factors in cache dirtiness, allowing the system to defer power gating when caches are dirty and flush would be costly, while still achieving power savings when appropriate.
2Productivity
If idle time interval before power gating is set to a relatively long time, then performance cost is reduced, but energy conservation efficiency is worsened
Solution Approach 1:
The patent implements feedback mechanisms that continuously monitor cache dirtiness metrics and use this information to dynamically adjust power gating decisions. The system collects data on dirty cache line counts, predicts idle time durations, and uses this feedback to make informed decisions about when to initiate power gating. This feedback loop allows the system to optimize the idle time interval dynamically rather than using a fixed long threshold, thereby improving energy conservation efficiency without incurring excessive performance costs.
Solution Approach 2:
The patent performs preliminary assessment of cache dirtiness and idle time prediction before making the power gating decision. By evaluating these metrics in advance, the system can determine the optimal timing for power gating, initiating the process at the right moment to minimize both energy waste and performance overhead. This preliminary action prevents both premature power gating (which would waste energy) and delayed power gating (which would incur performance costs).
Data Source
AI summary
Power gating decisions can be made based on measures of cache dirtiness. Analyzer logic can selectively power gate a component of a processor system based on a cache dirtiness of one or more caches associated with the component. The analyzer logic may power gate the component when the cache dirtiness exceeds a threshold and may maintains the component in an idle state when the cache dirtiness does not exceed the threshold. Idle time prediction logic may be used to predict a duration of an idle time of the component. The analyzer logic may then selectively power gates the component based on the cache dirtiness and the predicted idle time.