Cache Data Stashing Control Using Stash Interest Requests
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Solution Overview
Problem
Existing data processing systems face challenges in detecting appropriate scenarios for stashing data generated by one processing element in the local storage structure of another processing element, leading to significant latency and energy consumption due to memory accesses.
Innovation Solution
The implementation of a stashee hint instruction that generates control signals to issue a stash interest request, allowing updated data to be made available for stashing in an associated storage structure of the first processing element, using decoder and processing circuitry to manage data stashing through interconnect circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is written to memory for inter-processing-element availability, then data can be accessed by other processing elements, but latency and energy consumption increase significantly
Solution Approach 1:
The consumer processing element issues a stash interest request in advance before actually needing the data, allowing the system to prepare for potential data stashing. This preliminary action enables faster data retrieval when needed by pre-establishing the stashing mechanism rather than reacting to data needs after they arise.
Solution Approach 2:
The stash interest request acts as an intermediary signal between the consumer processing element and the stashing control circuitry. This intermediary mechanism coordinates the data stashing process without requiring direct memory accesses, thereby reducing latency while ensuring data availability.
2Reliability
If data is written to memory for inter-processing-element availability, then data can be accessed by other processing elements, but energy consumption increases significantly
Solution Approach 1:
By issuing the stash interest request in advance, the system prepares the data path and stashing mechanism before actual data retrieval is needed. This eliminates the need for high-energy memory accesses during critical data retrieval operations, as the stashing infrastructure is already in place and ready to transfer data directly between processing elements.
Solution Approach 2:
The stash interest request serves as an intermediary that enables direct data transfer mechanisms to be activated. This intermediary signal allows the system to use lower-energy direct transfer paths instead of high-energy main memory accesses, thereby reducing overall energy consumption while maintaining data availability.
3Extent of automation
If hardware automatically detects stashing scenarios, then data can be stashed without software intervention, but detecting appropriate scenarios becomes extremely difficult
Solution Approach 1:
The stash interest request creates a feedback mechanism where the consumer processing element actively signals its data needs to the stashing control circuitry. This feedback approach transforms the detection problem into an explicit communication problem, making it easier to identify when stashing is appropriate through direct signals rather than complex hardware inference.
Solution Approach 2:
The stash interest request acts as an intermediary signal that bridges the gap between software instructions and hardware stashing logic. This intermediary mechanism translates high-level data access needs into concrete stashing actions, simplifying the detection process by providing clear, unambiguous signals about when stashing should occur.
Data Source
AI summary
An apparatus has decoder circuitry within a first processing element to decode instructions, in order to respond to a sequence of instructions by generating control signals. Processing circuitry within the first processing element is responsive to the control signals to perform operations defined by the sequence of instructions. The decoder circuitry is responsive to a stashee hint instruction in the sequence of instructions to issue control signals to cause the processing circuitry to issue a stash interest request via an interface used to couple the first processing element to interconnect circuitry. The stash interest request is arranged to provide a given memory address indication determined from the stashee hint instruction and to trigger stashing control circuitry accessible via the interconnect circuitry to cause updated data associated with the given memory address indication to be made available for stashing in an associated storage structure of the first processing element.