Index Array Finite State Machine Scatter Gather Operations
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Solution Overview
Problem
Current technologies face performance bottlenecks and inefficiencies in memory access and data ordering for wide SIMD operations, particularly in scatter and gather operations, due to noncontiguous memory locations and page faults, which increase clock cycles and reduce instruction throughput.
Innovation Solution
The implementation of an index array and finite state machine facilitates scatter and gather operations by generating addresses and tracking completion masks without requiring multiple micro-operations, improving instruction throughput by parallel execution with other instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gather operations are implemented to collect data from noncontiguous memory locations, then data access flexibility is improved, but the number of clock cycles required increases due to multiple memory accesses and potential page faults
Solution Approach 1:
The patent applies preliminary action by saving the state of gather operations in a state save buffer before interruption occurs. When a page fault or interrupt happens during a gather operation, the saved state allows the operation to be restarted from the point of interruption rather than being repeated from the beginning, thereby reducing the clock cycles lost due to interrupts while maintaining the flexibility of accessing noncontiguous memory locations
Solution Approach 2:
The patent introduces an intermediary mechanism - a state save buffer - that stores the state information of gather operations. This intermediary structure enables the system to resume operations after interrupts without losing progress, effectively mediating between the need for flexible memory access and the cost of interrupt handling in terms of clock cycles
2Measurement precision
If completion masks are used to track completion of individual loads and stores, then operation tracking accuracy is improved, but device complexity increases due to additional physical register storage requirements
Solution Approach 1:
The patent applies universality by designing the state save buffer to serve multiple functions: it tracks completion of gather operations, stores state information for interruption recovery, and manages the coordination between multiple memory access operations. This multi-functional approach achieves precise operation tracking without requiring separate dedicated storage structures for each function, thereby reducing overall device complexity
Solution Approach 2:
The patent merges the completion mask functionality with the state save buffer mechanism. Instead of maintaining separate completion masks and state information, the buffer integrates both functions into a unified structure that tracks operation completion status while also preserving state for interruption recovery, reducing the total physical register storage required
3Adaptability or versatility
If scatter operations disperse elements to noncontiguous memory locations, then data organization flexibility is improved, but instruction throughput decreases due to serialization requirements for fault resolution
Solution Approach 1:
The patent applies preliminary action by pre-saving the state of scatter operations before interrupts occur. When page faults happen during scattered memory accesses, the saved state enables parallel recovery and continuation of multiple scatter operations rather than serial execution, thereby maintaining high instruction throughput while preserving the flexibility of dispersing data to noncontiguous memory locations
Data Source
AI summary
Methods and apparatus are disclosed for using an index array and finite state machine for scatter/gather operations. Embodiment of apparatus may comprise: decode logic to decode a scatter/gather instruction and generate a set of micro-operations, and an index array to hold a set of indices and a corresponding set of mask elements. A finite state machine facilitates the gather operation. Address generation logic generates an address from an index of the set of indices for at least each of the corresponding mask elements having a first value. An address is accessed to load a corresponding data element if the mask element had the first value. The data element is written at an in-register position in a destination vector register according to a respective in-register position the index. Values of corresponding mask elements are changed from the first value to a second value responsive to completion of their respective loads.