Address Translation Latency Measurement Circuitry
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Solution Overview
Problem
Existing data processing systems face challenges in accurately measuring and diagnosing performance issues related to address translation latency, which can vary significantly even for instructions experiencing the same events, such as TLB misses, due to varying caching strategies and complex page table structures, making it difficult to determine the true cost to performance.
Innovation Solution
Incorporating translation latency measuring circuitry to directly measure the latency of address translation processes, allowing for more accurate performance analysis by tracking the latency between specific start and end events, and using a two-stage address translation approach to support virtualization, while also sampling a subset of instructions to reduce overhead and provide targeted diagnostic information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If address translation latency is measured using event counting (TLB misses, page table walks), then the measurement approach is simple, but the measurement precision is insufficient because it does not capture the actual time taken
Solution Approach 1:
The patent introduces translation latency measuring circuitry as an intermediary component between the address translation circuitry and the performance monitoring system. This measuring circuitry captures start and end events of address translation processes and calculates actual latency values, serving as a mediator that transforms unmeasurable time intervals into quantifiable performance data without interfering with the core address translation function
Solution Approach 2:
The patent replaces the indirect mechanical counting approach (counting TLB misses and page table walks) with a direct temporal measurement system. Instead of using discrete event counters, the system uses timestamp-based latency measurement that directly captures the time duration of address translation operations, substituting a coarse mechanical counting mechanism with a precise temporal measurement mechanism
2Measurement precision
If all instructions are monitored for address translation latency, then the measurement completeness is high, but the productivity of the system decreases due to overhead
Solution Approach 1:
The patent implements partial monitoring by selecting a subset of instructions for latency measurement rather than monitoring all instructions. The translation latency measuring circuitry is configured to measure latency for selected instructions based on criteria such as instruction type or performance relevance, applying partial action to reduce overhead while maintaining sufficient measurement coverage for accurate performance analysis
Solution Approach 2:
The patent applies different monitoring strategies to different instructions based on their characteristics. Critical instructions that have significant impact on performance are monitored with high precision, while less critical instructions may use simplified monitoring or be excluded entirely. This local differentiation of monitoring quality optimizes the balance between measurement accuracy and system overhead
3Adaptability or versatility
If address translation latency varies due to caching strategies and page table structures, then the system adaptability is high, but the difficulty of detecting and measuring the true latency increases
Solution Approach 1:
The patent segments the address translation process into distinct measurable events: start events (such as virtual address request initiation) and end events (such as translated address return or data access request). By dividing the complex address translation process into discrete segments with clear boundary events, the system can accurately measure latency regardless of the internal implementation details of caching strategies or page table structures
Solution Approach 2:
The translation latency measuring circuitry implements feedback by continuously monitoring actual latency values and using this information to identify performance bottlenecks. The measured latency data provides feedback about the effectiveness of caching strategies and page table structures, enabling dynamic optimization and adjustment of these components based on actual performance characteristics
Data Source
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AI summary
An apparatus includes processing circuitry to process instructions, some of which may require addresses to be translated. The apparatus also includes address translation circuitry to translate addresses in response to instruction processed by the processing circuitry. Furthermore, the apparatus also includes translation latency measuring circuitry to measure a latency of at least part of an address translation process performed by the address translation circuitry in response to a given instruction.