Unaligned Memory Access Concurrency via Segmentation
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Solution Overview
Problem
Conventional memory access methods fail to guarantee block concurrency when accessing data that is not naturally aligned, leading to potential partial updates and inconsistencies, especially when multiple CPUs access the same memory locations simultaneously.
Innovation Solution
The solution involves accessing memory data in aligned groups based on the address alignment size, ensuring that each group is accessed as a single unit, even if the address is not integral to the memory reference size, by using modified memory reference instructions that provide different levels of block concurrency, such as byte, two-byte, four-byte, and eight-byte concurrency, depending on the alignment size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If vector load and store instructions are used for unaligned memory accesses, then access speed is improved, but consistency and block concurrency are not guaranteed
Solution Approach 1:
The patent segments unaligned memory access into multiple aligned access operations. When a vector load/store instruction cannot provide block concurrency for unaligned addresses, the system breaks down the unaligned access into multiple smaller aligned accesses that can be executed with consistency guarantees, then combines the results to achieve the desired unaligned access effect.
2Productivity
If multiple CPUs access the same memory locations simultaneously without alignment guarantees, then processing parallelism is improved, but partial updates and data inconsistencies occur
Solution Approach 1:
The patent performs preliminary alignment analysis before executing memory access operations. By determining the alignment characteristics of memory addresses in advance, the system can pre-plan the access strategy (whether to use vector instructions or segmented aligned accesses), ensuring that subsequent parallel operations maintain consistency without requiring runtime synchronization overhead.
3Device complexity
If conventional memory access methods are used for unaligned addresses, then implementation simplicity is maintained, but block concurrency cannot be guaranteed
Solution Approach 1:
The patent implements a dynamic memory access method that adapts to the alignment characteristics of each access request. The system dynamically selects between different access strategies (vector instructions for aligned accesses, segmented aligned accesses for unaligned accesses) based on real-time analysis of address alignment, providing both simplicity for aligned cases and reliability for unaligned cases without requiring complex static configuration.
Data Source
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AI summary
A method for accessing data in a memory coupled to a processor comprising: receiving a memory reference instruction for accessing data of a first size at an address in the memory; determining an alignment size of the address in the memory; and accessing the data of the first size in one or more groups of data by accessing each group of data block concurrently. The groups of data have sizes that are multiples of the alignment size.