History-Based Speculative Read Control for Partitioned Cache Memories
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In computing systems with shared cache memories, speculative reads often result in high memory bandwidth consumption and power usage due to repeated discards of data when the requested data is found in another cache partition, leading to inefficiencies in latency reduction and performance.
Innovation Solution
A method and apparatus for operating a cache memory with partitions, where history data is used to determine the source of previous read requests, and a speculative read is initiated only if the source is less than a predetermined threshold, optimizing memory bandwidth and power usage by reducing unnecessary reads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If speculative reads are performed to reduce latency when data is not found in the first partition, then latency is reduced, but memory bandwidth consumption and power usage increase due to repeated discards of data
Solution Approach 1:
The patent implements a history register that stores information about the source of returned data from previous read requests. This feedback mechanism allows the system to learn from past access patterns and make informed decisions about whether to perform speculative reads, thereby reducing unnecessary memory accesses while maintaining low latency for valid speculative reads.
Solution Approach 2:
The patent performs preliminary checks by reading the history register before initiating speculative reads. This preliminary action determines whether a speculative read is likely to succeed based on historical data, preventing unnecessary speculative reads that would consume memory bandwidth and power without providing latency benefits.
2Loss of time
If speculative reads are performed to reduce latency, then latency is reduced, but the number of unnecessary memory reads increases when data is found in another partition
Solution Approach 1:
The history register provides feedback about previous read outcomes, storing whether data was returned from another partition or from memory. This feedback enables the system to distinguish between productive speculative reads (those that find data in another partition) and unproductive ones (those that would require memory access), thereby improving overall memory read efficiency while maintaining latency benefits.
Solution Approach 2:
The system uses its own historical access patterns to make decisions about future speculative reads. By examining the history register, the system serves itself by determining whether speculative reads are likely to be successful, eliminating the need for external control mechanisms and improving memory read efficiency autonomously.
Data Source
AI summary
A cache memory that selectively enables and disables speculative reads from system memory is disclosed. The cache memory may include a plurality of partitions, and a plurality of registers. Each register may be configured to stored data indicative of a source of returned data for previous requests directed to a corresponding partition. Circuitry may be configured to receive a request for data to a given partition. The circuitry may be further configured to read contents of a register corresponding to the given partition, and initiate a speculative read dependent upon the contents of the register.