SMT Processor Usage Estimation via Thread State Sampling
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Solution Overview
Problem
Simultaneous Multi-Threading (SMT) processors distort CPU usage measurements, leading to inaccurate throughput estimates, which can result in misperceptions about processing capacity and impact system performance and capacity planning.
Innovation Solution
A method and system to determine a CPU usage adjustment factor by sampling CPU usage and thread states, deriving a distribution of running threads, and applying an adjustment factor to provide a more accurate CPU usage estimate for SMT processors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If SMT processors execute multiple threads in parallel to improve throughput, then processor throughput is improved, but CPU usage measurements become distorted and less accurate
Solution Approach 1:
The patent applies feedback by continuously monitoring actual thread execution states and using this information to adjust CPU usage measurements. The system samples thread states at intervals and uses the distribution of observed thread counts to calculate correction factors that feedback into the CPU usage reporting mechanism, thereby compensating for the distortion caused by SMT parallel execution.
Solution Approach 2:
The patent changes the parameter of CPU usage measurement by introducing correction factors derived from thread state distributions. Instead of directly reporting raw CPU usage percentages, the system transforms these values using parameters calculated from observed thread execution patterns, converting distorted measurements into corrected estimates that reflect actual processor utilization more accurately.
2Loss of information
If operating systems report CPU usage on SMT processors, then system monitoring is enabled, but the reported usage does not reflect actual processing capacity
Solution Approach 1:
The patent introduces an intermediary correction mechanism between the operating system's raw CPU usage reporting and the final reported values. This intermediary layer samples thread states, calculates distribution-based correction factors, and applies these factors to bridge the gap between uncorrected OS reports and accurate utilization estimates, thereby maintaining information availability while improving reliability.
Solution Approach 2:
The patent substitutes the mechanical (direct) reporting mechanism with a statistical correction mechanism. Instead of directly trusting raw CPU usage percentages, the system replaces this direct reporting with a statistical model that samples thread states and computes corrected values based on observed execution patterns, thereby improving reliability without losing monitoring capability.
3Extent of automation
If capacity planners use reported CPU usage data for forecasting, then planning decisions can be made, but the forecasts are inaccurate due to measurement distortion
Solution Approach 1:
The patent applies preliminary action by pre-calculating correction factors based on thread state distributions before capacity planning decisions are made. The system continuously samples thread execution patterns and maintains updated correction factor tables that can be applied in advance to forecasted data, ensuring that capacity planners receive accurate utilization estimates without manual intervention to adjust for SMT distortion.
Data Source
AI summary
Methods and systems are disclosed for determining a processor usage adjustment factor and for automatically applying the processor usage adjustment factor to provide a processor usage estimate for an SMT processor. In one implementation, the methods and systems obtain samples of processor usage reported by the operating system at a predefined sampling rate over a predefined sampling interval. Thread states for the threads substantially corresponding to the reported processor usage are so obtained at the predefined sampling rate and over the predefined sampling interval. This sampling may be performed for servers running different applications and having diverse processing loads. An estimate of the distribution of the number of threads running for the processor usage reported may then be determined from the sampled data. A processor usage adjustment factor may then be derived, based on the distribution, and used to provide a processor usage estimate.