Processor Performance Monitoring Unit Prefetch Instruction Retirement Counting
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Solution Overview
Problem
Current processor performance monitoring mechanisms lack the ability to specifically track and count retired prefetch instructions, which hinders efficient performance analysis and optimization in micro-architectural designs.
Innovation Solution
Implementing dedicated counters within a processor to maintain separate counts for prefetch and non-prefetch instructions, with filter rules to conditionally include or exclude retirement events, allowing for precise monitoring of prefetch instruction retirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated counters are implemented to track prefetch instructions separately, then measurement precision of prefetch instruction retirement is improved, but device complexity increases
Solution Approach 1:
The counter is divided into separate fields: a first counter field for tracking prefetch instructions and a second counter field for tracking non-prefetch instructions. This segmentation allows independent monitoring of each instruction type, enabling precise measurement of prefetch instruction retirement without requiring entirely separate hardware for each counter.
Solution Approach 2:
Filter rules are applied selectively to specific instruction types rather than uniformly to all instructions. The system uses local filtering logic that examines instruction characteristics and applies appropriate counting rules based on the specific instruction being retired, rather than using a global filtering mechanism.
2Measurement precision
If filter rules are implemented to conditionally include or exclude retirement events, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The performance monitoring system automatically applies filter rules based on instruction characteristics without requiring manual intervention. The system self-configures which retirement events to count or exclude by examining instruction type identifiers and applying pre-defined filter criteria, eliminating the need for operators to manually configure or interpret complex filtering settings.
Solution Approach 2:
The system provides feedback through separate counter fields that clearly indicate the retirement count for prefetch versus non-prefetch instructions. This feedback mechanism presents processed information in a differentiated, easily interpretable format that directly reflects the application of filter rules, making the results immediately useful without requiring additional analysis or manual filtering.
Data Source
AI summary
Techniques and mechanisms for circuitry of a processor to determine a count of prefetch instructions which have been retired, or are designated for retirement. In an embodiment, a performance monitoring unit (PMU) monitors the execution of an instruction sequence by a core of said processor. The PMU detects the retirement of a first instruction, and further makes a first determination that the instruction is of a prefetch instruction type. Based on the first determination, counter circuitry of the processor updates a count of one or more instruction retirements, wherein each such retired instruction is of the prefetch instruction type. The PMU further makes a second determination that another retired second instruction is of a non-prefetch instruction type. In another embodiment, the counter circuitry prevents any updating of that same count based on the second determination.