Processor Core Cache Recovery After Cold Start
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Solution Overview
Problem
During a processor reset, data in cache memories and branch prediction tables is lost, leading to performance hindrance as these resources take time to refill with valid data, especially after power-on resets or reduced power mode recoveries.
Innovation Solution
A control circuit is configured to pre-fetch and store instruction data and allocate branch prediction entries at increased rates after a reset, adjusting based on available storage and allocation success, to quickly repopulate cache memories and branch prediction tables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the processor enters a reduced power mode to save energy, then power consumption is reduced, but data in cache memories and branch prediction tables is lost requiring time-consuming refilling
Solution Approach 1:
The patent applies preliminary action by detecting when cache memory or branch prediction table resources are becoming depleted and initiating pre-fetch operations to load additional data before the resources are completely exhausted. This proactive approach ensures that refilling begins earlier, reducing the performance penalty after power mode transitions.
2Reliability
If the processor refills cache memories and branch prediction tables at normal rates after reset, then resource utilization is maintained, but processor performance is hindered during the refill period
Solution Approach 1:
The patent implements dynamics by dynamically adjusting the pre-fetch rate based on the detected resource level. When cache or branch prediction table resources are low, the system increases the pre-fetch rate to rapidly replenish resources. This adaptive approach balances resource utilization with processor performance by optimizing the refill speed according to current system conditions.
3Loss of time
If pre-fetch operations are continuously performed at high rates, then cache and branch prediction tables are refilled quickly, but unnecessary pre-fetch operations consume additional energy and bandwidth
Solution Approach 1:
The patent applies feedback by continuously monitoring the resource levels in cache memories and branch prediction tables, using this information to dynamically adjust the pre-fetch rate. When resources are充足的, the pre-fetch rate is reduced or suspended; when resources are depleted, the rate is increased. This feedback-driven approach ensures pre-fetch operations are performed at appropriate rates, avoiding unnecessary energy consumption while maintaining effective refill timing.
Data Source
AI summary
In an embodiment, an apparatus includes a cache memory and a control circuit. The control circuit may be configured to pre-fetch and store a first quantity of instruction data in response to a determination that a first pre-fetch operation request is received after a reset and prior to a first end condition. The first end condition may depend on an amount of unused storage in the cache memory. The control circuit may be further configured to pre-fetch and store a second quantity of instruction data in response to a determination that a second pre-fetch operation request is received after the first end condition. The second quantity may be less than the first quantity.