TLB Overlap Checking Hardware Mechanism
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Solution Overview
Problem
Current systems face challenges in maintaining data consistency and reliability in translation lookaside buffers (TLBs) due to programming errors and complexities introduced by multiple operating systems, particularly in managing overlapping virtual address translations.
Innovation Solution
Implementing processor-level hardware-based overlap checking using instructions like the overlap check and conditional TLB write instructions, which determine if creating a new entry in the TLB would result in overlapping pages, thereby preventing data inconsistencies and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If software-based overlap checking is used in the operating system, then data consistency can be maintained, but the system complexity increases and programming errors may occur
Solution Approach 1:
The patent introduces a dedicated overlap checking mechanism as an intermediary component between the TLB management software and the hardware TLB structure. This intermediary performs specialized overlap detection functions, separating the complexity of overlap checking from the general operating system TLB management code, thereby reducing overall system complexity while maintaining reliability through specialized error-free checking logic
Solution Approach 2:
The overlap checking function is extracted from the operating system's TLB management software and implemented as a separate hardware-assisted feature. By taking out the overlap checking duty from software and implementing it through dedicated hardware logic triggered by specific instructions, the patent eliminates programming errors in software-based checking while reducing the complexity of operating system code
2Adaptability or versatility
If multiple operating systems concurrently execute with TLB management, then system versatility increases, but the difficulty of detecting and preventing overlapping translations increases
Solution Approach 1:
The patent implements preliminary overlap checking before allowing TLB entries to be created or modified. The overlap check instruction is executed in advance of any TLB write operations, detecting potential overlaps between virtual address translations across multiple operating systems before they can cause conflicts. This preliminary detection prevents overlapping translations from occurring in the first place
Solution Approach 2:
The patent implements a feedback mechanism where the overlap checking logic provides immediate information back to the processor about detected overlaps. When the overlap check instruction is executed, the processor receives feedback indicating whether overlapping translations exist, allowing the system to make informed decisions about TLB entry creation or modification while supporting multiple concurrent operating systems
3Productivity
If hardware-based overlap checking is implemented, then processing speed increases, but the device complexity increases
Solution Approach 1:
The patent implements hardware overlap checking logic that mirrors or copies the essential overlap detection functionality needed, rather than implementing a completely new complex system. The hardware logic replicates the comparison and detection operations that would otherwise be performed in software, providing speed improvement through hardware execution while keeping the added complexity minimal by copying only the necessary checking functions
Solution Approach 2:
The patent enables the processor to perform self-checking for TLB overlap conditions through the overlap check instruction. The hardware-based checking mechanism allows the processor to autonomously detect overlapping translations without requiring external software intervention, improving processing speed through immediate hardware-level detection while the self-service nature limits the additional complexity to only the essential checking logic
Data Source
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AI summary
An apparatus includes a translation lookaside buffer (TLB). The TLB includes at least one entry that includes an entry virtual address and an entry page size indication corresponding to an entry page. The apparatus also includes input logic configured to receive an input page size indication and an input virtual address corresponding to an input page. The apparatus further includes overlap checking logic configured to determine, based at least in part on the entry page size indication and the input page size indication, whether the input page overlaps the entry page.