SLAT Memory Slab Layout to Reduce Address Translation Lookups
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Solution Overview
Problem
The inefficiencies in memory access within virtual machines due to the traversal of multiple hierarchical levels in the Second Layer Address Table (SLAT) lead to slower memory access times, discouraging the use of virtual machines despite their security benefits.
Innovation Solution
Implementing slabs of memory with uniform access permissions to allow direct identification by higher-level SLAT entries, thereby skipping lower-level table lookups and optimizing SLAT traversal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple hierarchical levels of SLAT tables are traversed to map virtual machine memory addresses to physical memory addresses, then memory address translation accuracy is improved, but memory access time increases
Solution Approach 1:
The patent segments the SLAT into multiple hierarchical levels (e.g., root table, level 1 tables, level 2 tables) where each level handles a portion of the address translation. This segmentation allows accurate translation of large address spaces while enabling parallel lookup paths that can be optimized to reduce traversal time.
Solution Approach 2:
The patent introduces a new dimension to the address translation process by implementing alternative lookup paths, such as direct mapping for certain memory regions or using metadata caches that store frequently accessed translations. This adds dimensional flexibility to the translation process, allowing the system to choose faster paths when accuracy requirements are met.
2Reliability
If virtual machines are used to provide security benefits, then system security is improved, but memory access performance deteriorates
Solution Approach 1:
The patent performs preliminary actions by pre-translating and caching memory address mappings in metadata structures before they are needed during runtime. This allows the system to maintain security through proper address translation while reducing the performance impact by having translations ready in advance.
Solution Approach 2:
The patent introduces intermediary data structures (metadata tables, caching mechanisms) that mediate between the virtual machine's memory access requests and the physical memory. These intermediaries enable security checks to be performed without requiring full traversal of the hierarchical SLAT for every access, thus maintaining security while improving performance.
3Adaptability or versatility
If hierarchical SLAT tables are implemented to manage large memory spaces, then memory management capability is improved, but device complexity increases
Solution Approach 1:
The patent implements universal data structures and algorithms that can handle different memory management scenarios with the same hierarchical SLAT framework. This multi-functionality allows the system to manage various types of memory (physical, virtual, shared) through a unified structure, reducing the apparent complexity despite the enhanced capabilities.
Solution Approach 2:
The patent introduces dynamic characteristics to the SLAT structure, allowing it to adapt its complexity based on runtime requirements. For example, certain hierarchical levels can be collapsed or bypassed when not needed, and the structure can be dynamically configured to optimize for specific workloads, making the complexity manageable while maintaining high adaptability.
Data Source
AI summary
To increase the speed with which a Second Layer Address Table (SLAT) is traversed, memory having the same access permissions is contiguously arranged such that one or more hierarchical levels of the SLAT need not be referenced, thereby resulting in more efficient SLAT traversal. “Slabs” of memory are established whose memory range is sufficiently large that reference to a hierarchically lower level table can be skipped and a hierarchically higher level table's entries can directly identify relevant memory addresses. Such slabs are aligned to avoid smaller intermediate memory ranges. The loading of code or data into memory is performed based on a next available memory location within a slab having equivalent access permissions, or, if such a slab is not available, or if an existing slab does not have a sufficient quantity of available memory remaining, a new slab with the proper access permissions is established.