Processor Offload Queue for Remote PIM Execution
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Solution Overview
Problem
Current computing systems face inefficiencies in processing performance and energy consumption due to high data movement and memory-bound phases, particularly in applications with low temporal data reuse and low computational intensity, where offloading to a Processing-in-Memory (PIM) device can reduce latency and power consumption but is complicated by threading model changes and atomicity enforcement.
Innovation Solution
The solution involves hardware and instruction set architecture support for offloading computations to PIM devices or accelerators without changing the threading model, enabling cacheable, coherent data offloading and reducing complexity by using an offload queue with metadata management to ensure data integrity and order, suitable for out-of-order, multiple-issue CPU cores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If computations are offloaded to PIM devices, then energy consumption and latency are reduced, but device complexity and orchestration overhead increase
Solution Approach 1:
The patent introduces an offload queue as an intermediary structure between the processor and PIM device. This queue manages offload instructions and coordinates data transfer, simplifying the orchestration complexity while enabling energy-efficient computation offloading. The queue acts as a buffer that decouples the processor from the PIM device, reducing the overhead of direct coordination.
2Measurement precision
If data is frequently fetched from memory due to low cache reuse, then computational accuracy is maintained, but performance and energy efficiency deteriorate
Solution Approach 1:
The patent implements preliminary action by pre-loading data into the offload queue before computation is needed. The system identifies data that will be used in upcoming computations and prepares it for transfer to the PIM device in advance, reducing the need for frequent cache misses and improving performance while maintaining computational accuracy.
Solution Approach 2:
The patent moves computation from the traditional CPU-cache-memory hierarchy to a parallel dimension by utilizing PIM devices. This dimensional shift allows computations to occur closer to the data in memory, bypassing the limitations of the cache hierarchy and improving performance without sacrificing accuracy.
3Speed
If computations are offloaded to remote devices, then processing speed is improved, but data dependency management becomes more difficult
Solution Approach 1:
The patent implements feedback mechanisms where the offload queue monitors the status of offloaded computations and adjusts subsequent data transfers accordingly. This feedback loop ensures that data dependencies are properly managed by coordinating data movement with computation progress, maintaining processing speed while simplifying dependency management.
Data Source
AI summary
Offloading computations from a processor to remote execution logic is disclosed. Offload instructions for remote execution on a remote device are dispatched in the form of processor instructions like conventional instructions. In the processor, an offload instruction is inserted in an offload queue. The offload instruction may be inserted at the dispatch stage or the retire stage of the processor pipeline. Metadata for the offload instruction is added to the offload instruction in the offload queue. After retirement of the offload instruction, the processor transmits an offload request generated from the offload instruction.