Stash Hint Instruction for Low-Latency Data Sharing
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Solution Overview
Problem
Existing data processing systems face challenges in detecting scenarios where data generated by one processing element should be stashed in the local storage structure of another processing element, leading to significant latency and energy consumption due to memory accesses.
Innovation Solution
Implementing a stash hint instruction within a processing element's decoder circuitry to initiate a modified data update transaction, which identifies a memory address for data stashing in associated storage structures of other processing elements, facilitated by stashing control circuitry and interconnect circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is written to memory to be accessed by another processing element, then data availability is ensured, but latency and energy consumption increase significantly
Solution Approach 1:
The stash hint instruction enables the producing processing element to proactively push data to the consuming processing element's storage structure before the consumer actually needs it. This preliminary action eliminates the subsequent latency of the consumer fetching data from memory, as the data is already available in the consumer's local storage when needed.
Solution Approach 2:
The stash mechanism acts as an intermediary between the producing and consuming processing elements. Instead of direct memory access or waiting for the consumer to request data, the producer can directly stash data in the consumer's storage structure through the interconnect, serving as a mediator that reduces communication latency and memory access overhead.
2Reliability
If data is written to memory to be accessed by another processing element, then data availability is ensured, but energy consumption increases significantly
Solution Approach 1:
By proactively stashing data in the consuming processing element's storage structure before it is needed, the system avoids subsequent energy-consuming memory accesses. The preliminary push operation consumes less energy than the combination of memory write followed by memory read, as it utilizes the more energy-efficient interconnect path.
Solution Approach 2:
The stash mechanism serves as an energy-efficient intermediary path for data transfer. By routing data through the interconnect directly to the consumer's storage structure rather than through main memory, the system reduces the energy consumption associated with memory accesses while ensuring data availability.
3Productivity
If hardware automatically detects stashing opportunities, then data stashing efficiency improves, but device complexity increases
Solution Approach 1:
Instead of requiring complex hardware to automatically detect and manage stashing opportunities, the system uses software (stash hint instruction) to explicitly indicate when stashing should occur. This self-service approach shifts the detection burden from hardware to software, maintaining high stashing efficiency while reducing hardware complexity.
Solution Approach 2:
The stash hint instruction acts as an intermediary mechanism that bridges software intent and hardware action. Rather than requiring complex hardware detection logic, the software explicitly signals stashing opportunities through the hint instruction, which the hardware then executes. This intermediary approach simplifies hardware design while maintaining productivity.
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 stash hint instruction associated with a given data update instruction in the sequence of instructions, to issue control signals to cause the processing circuitry to respond to the given data update instruction by initiating a modified data update transaction via an interface used to couple the first processing element to interconnect circuitry. The modified data update transaction identifies a given memory address to which updated data is to be written in response to the given data update instruction, and triggers stashing control circuitry accessible via the interconnect circuitry to cause the updated data to be made available for stashing in an associated storage structure of at least one further processing element coupled to the interconnect circuitry.