Parallel Processing Request Coalescing for Constant-Data Multicast
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Solution Overview
Problem
Conventional parallel processing units (PPUs) face bandwidth issues and complexity in servicing multiple threads requesting the same constant data, leading to inefficiencies in writeback bandwidth and increased latency due to address matching and synchronization requirements.
Innovation Solution
A PPU employs a request coalescer to coalesce writeback requests using reduced bit identifiers, leveraging generic writeback buffers to multicast constant data to uniform registers without synchronizing individual cores, thereby reducing bandwidth requirements and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional parallel processing units service multiple threads requesting the same constant data individually, then each thread receives its data, but bandwidth consumption increases and latency increases due to address matching and synchronization requirements
Solution Approach 1:
The patent merges multiple identical writeback requests into a single multicast operation. When multiple threads request the same constant data, the system combines these requests and delivers the data once to all requesting threads simultaneously, rather than servicing each thread individually. This merging approach maintains complete data delivery to all threads while dramatically reducing bandwidth consumption by eliminating redundant data transmissions.
Solution Approach 2:
The patent implements a universal writeback mechanism that can handle both individual thread requests and multicast requests to multiple threads. The system uses a request coalescer that identifies when multiple threads request the same data and automatically switches to a multicast mode, making the writeback mechanism universally applicable to different request patterns. This multi-functionality allows the system to optimize bandwidth usage dynamically based on request patterns while ensuring all threads receive their required data.
2Reliability
If conventional parallel processing units service multiple threads requesting the same constant data with address matching and synchronization, then data is delivered to all threads, but system complexity increases
Solution Approach 1:
The patent extracts the address matching and synchronization functions from the individual thread writeback process and consolidates them into a centralized request coalescer. This coalescer pre-processes writeback requests, identifies identical data requests, and groups them together before the actual data transfer. By taking out these complex functions and centralizing them, the system reduces the complexity burden on individual thread handling paths while ensuring complete and synchronized data delivery to all requesting threads.
Solution Approach 2:
The patent performs preliminary analysis and grouping of writeback requests before the actual data transfer occurs. The request coalescer examines incoming writeback requests, identifies when multiple threads request the same constant data, and prepares a consolidated multicast operation in advance. This preliminary action eliminates the need for complex real-time address matching and synchronization during the critical data transfer phase, thereby reducing overall system complexity while maintaining data delivery reliability.
3Loss of energy
If reduced bit identifiers are used to coalesce writeback requests, then bandwidth requirements decrease and process simplification occurs, but request identification capability must be maintained
Solution Approach 1:
The patent uses compact identifiers that capture the essential information needed to identify unique data requests without requiring full address information. Instead of copying or transmitting complete memory addresses, the system uses reduced-bit identifiers that uniquely identify constant data requests. These identifiers are sufficient for the request coalescer to group identical requests together while using significantly fewer bits than full addresses, thereby reducing bandwidth consumption while maintaining accurate request identification and grouping capability.
Data Source
AI summary
A first instruction to load a first data into a first register file associated with a first subpartition unit is received. A second instruction to load the first data into a second register file associated with a second subpartition unit is received. The first instruction and the second instruction are coalesced into a first entry of a request coalescer based on instruction identifiers. The first entry is associated with the first data. Responsive to a determination that the first data is available in the cache, the first data is multicast from the cache to the first register file and the second register file.