Hardware Prefetch Tablewalks with Lowest Priority
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Solution Overview
Problem
Conventional hardware prefetch operations in microprocessors can block software-based tablewalks due to higher priority and are limited by page boundaries, leading to inefficiencies and potential resource wastage.
Innovation Solution
A hardware prefetch tablewalk system with a lowest priority engine that performs boundless and ageless operations, allowing software-based tablewalks to maintain higher priority and avoiding interruptions during architectural state updates, while ignoring page boundaries for more extensive prefetch patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hardware prefetch operations are given higher priority to improve prefetching efficiency, then prefetch performance is improved, but software-based tablewalks are blocked causing resource wastage
Solution Approach 1:
The patent changes the priority parameter of hardware prefetch tablewalks from high to low, allowing software-based tablewalks to complete first. This parameter change resolves the contradiction by preventing resource wastage while still enabling prefetch operations to execute subsequently, maintaining prefetch performance without blocking critical software requests.
2Productivity
If hardware prefetch tablewalks are allowed to proceed without interruption to improve prefetch efficiency, then prefetching performance is improved, but software requests may be delayed causing loss of time
Solution Approach 1:
The patent implements preliminary action by allowing software-based tablewalks to complete their critical operations first before hardware prefetch tablewalks begin execution. This sequencing ensures that time-sensitive software requests are handled without delay, while prefetch operations still proceed subsequently to improve overall efficiency.
3Adaptability or versatility
If hardware prefetch operations ignore page boundaries to enable boundless prefetching, then prefetch coverage is improved, but tablewalk complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the tablewalk operation into distinct phases: software-based tablewalks handle critical address translations first, followed by hardware prefetch tablewalks that can then ignore page boundaries. This segmentation allows boundless prefetching coverage while managing complexity through ordered execution rather than complex simultaneous handling.
Data Source
AI summary
A hardware prefetch tablewalk system for a microprocessor including a tablewalk engine that is configured to perform hardware prefetch tablewalk operations without blocking software-based tablewalk operations. Tablewalk requests include a priority value, in which the tablewalk engine is configured to compare priorities of requests in which a higher priority request may terminate a current tablewalk operation. Hardware prefetch tablewalk requests having the lowest possible priority so that they do not bump higher priority tablewalk operations and are bumped by higher priority tablewalk requests. The priority values may be in the form of age values indicative of relative ages of operations being performed. The microprocessor may include a hardware prefetch engine that performs boundless hardware prefetch pattern detection that is not limited by page boundaries to provide the hardware prefetch tablewalk requests.