Shared Page Tables for Accelerator-Specific Attribute Mapping
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Solution Overview
Problem
Conventional page table formats struggle to express accessibility attributes for accelerator devices, leading to inefficient communication bandwidth consumption and increased memory management overhead due to duplicated mapping operations across different accelerator devices.
Innovation Solution
Implement a memory management unit that maintains two sets of page tables: architectural page tables with fixed formats and extendable page tables with flexible formats, allowing for efficient translation and retrieval of both architecturally defined and extended accessibility attributes without duplicating mapping operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate per-accelerator page tables are maintained for each accelerator device, then accelerator-specific extended attributes can be specified, but communication bandwidth consumption increases and memory management overhead increases due to duplicated mapping operations
Solution Approach 1:
The patent merges the page table maintenance function to a single memory management unit that serves multiple accelerator devices. Instead of each accelerator maintaining its own separate page tables, a shared page table structure is implemented where the memory management unit centralizes the mapping operations. This eliminates the duplication of mapping operations across multiple accelerators while still allowing each accelerator to access the necessary extended attributes through the shared structure, thereby reducing communication bandwidth consumption.
Solution Approach 2:
The patent implements a universal page table structure that serves multiple accelerator devices simultaneously. The memory management unit maintains a single set of page tables that can be accessed by any accelerator device in the system. This universal structure allows different accelerator types to share the same mapping infrastructure while still retrieving their specific extended attributes, eliminating the need for separate per-accelerator page table implementations.
2Adaptability or versatility
If separate per-accelerator page tables are maintained for each accelerator device, then accelerator-specific extended attributes can be specified, but memory management overhead increases due to duplicated mapping operations
Solution Approach 1:
The patent consolidates the memory management functionality into a single memory management unit that handles page table maintenance for all accelerator devices. By merging the previously distributed page table management responsibilities into one centralized unit, the system eliminates redundant mapping operations and reduces the overall complexity of memory management. The shared page table structure allows the memory management unit to service multiple accelerators without requiring each accelerator to independently maintain its own page tables.
3Device complexity
If conventional page table formats are used, then architectural simplicity is maintained, but extended accessibility attributes for accelerator devices cannot be expressed
Solution Approach 1:
The patent segments the page table structure into distinct fields: conventional fields that maintain architectural compatibility and extended fields that provide accelerator-specific attributes. The page table entries are divided such that existing architectural page table formats remain intact for base functionality, while additional extended attribute fields are appended or integrated. This segmentation allows the system to preserve simple conventional page table operations while simultaneously expressing extended accessibility attributes needed by accelerator devices.
Solution Approach 2:
The patent implements a nested page table structure where extended attribute information is embedded within or alongside the conventional page table entries. The extended attributes are nested within the page table framework, allowing the conventional page table format to remain the outer structure while containing additional extended attribute data within its entries. This nesting enables both the simplicity of conventional formats and the expressiveness of extended attributes to coexist.
Data Source
AI summary
In accordance with the described techniques for extended attributes for shared page tables, a device includes an accelerator device and a memory management unit that maintains a first set of page tables and a second set of page tables. The second set of page tables includes extended attributes for accessing data that the accelerator device operates on. The memory management unit is configured to receive a virtual memory address, and translate the virtual memory address to a physical memory address using the first set of page tables. In addition, the memory management unit retrieves the extended attributes from the second set of page tables. In this way, data is accessed from the physical memory address based on the extended attributes.