Address Translation Circuitry Context Switching Latency
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Solution Overview
Problem
Current data processing systems face inefficiencies in address translation due to the need for multiple memory accesses during context switching and page table walks, which can lead to delays and incorrect translations during the switching of tasks and applications.
Innovation Solution
The implementation of address translation circuitry that can dynamically switch between hierarchical sets of address translation tables, allowing for efficient address translations by overwriting table definition data and executing test instructions to ensure correct translations before and after the switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple memory accesses are performed during address translation, then translation accuracy can be maintained, but translation latency increases
Solution Approach 1:
The patent stores multiple candidate translation table sets in advance in memory, preparing them before they are needed. When a context switch occurs, the MMU can immediately switch to a pre-prepared translation table set without performing multiple sequential memory accesses, thus reducing translation latency while maintaining accuracy through pre-validation of the candidate tables
Solution Approach 2:
The patent implements dynamic switching between multiple translation table sets based on context requirements. The MMU can dynamically select and switch between different translation table sets stored in memory, allowing flexible adaptation to different execution contexts while avoiding the need for multiple sequential memory accesses, thereby reducing latency
2Adaptability or versatility
If translation tables are switched during context switching, then multiple applications can share processing elements, but incorrect translations may occur during the switch
Solution Approach 1:
The patent incorporates validation mechanisms that verify the correctness of translation table switches. The system checks whether the switched translation tables are appropriate for the current execution context and validates that translations remain correct after switching, providing feedback to ensure reliability during context transitions
Solution Approach 2:
The patent prepares and validates candidate translation table sets in advance before context switching occurs. By pre-validating the correctness of translation tables and ensuring they are appropriate for the target context, the system cushions against potential incorrect translations during the switching process
3Ease of operation
If hierarchical translation tables are used, then address space organization is improved, but multiple memory accesses are required increasing complexity
Solution Approach 1:
The patent pre-loads and organizes hierarchical translation table sets in memory before they are needed for address translation. By preparing the hierarchical structure in advance and storing complete table sets, the system maintains good address space organization while reducing the need for multiple sequential memory accesses during actual translation operations
Data Source
AI summary
Data processing apparatus comprises one or more processing elements to execute processing instructions; address translation circuitry to perform address translations between a virtual address space and a physical address space, the address translations being defined by a current hierarchical set of address translation tables selected from two or more hierarchical sets of address translation tables, the address translation circuitry being responsive to current table definition data providing at least a pointer to a memory location of the current hierarchical set of address translation tables; the one or more processing elements being configured to overwrite the current table definition data with second table definition data providing at least a pointer to a memory location of a second, different, hierarchical set of address translation tables of the two or more hierarchical sets of address translation tables; the one or more processing elements being configured to execute test instructions requiring address translation before and after the overwriting of the current table definition data by the control circuitry and to detect whether the address translations required by the test instructions are correctly performed.