The Performance Engineering team at GitHub assessed how CPU performance degrades as utilization increases and how this relates to capacity.
Overview
The article discusses the relationship between CPU utilization and system performance, highlighting how increased CPU usage can lead to higher latency. It details the experiments conducted by the GitHub Performance Engineering team to identify optimal CPU utilization thresholds for maintaining performance while optimizing resource usage.
What You'll Learn
1
How to assess the impact of CPU utilization on system performance
2
Why maintaining optimal CPU utilization is crucial for performance efficiency
3
How to identify the 'Golden Ratio' of CPU utilization for your workloads
Prerequisites & Requirements
- Understanding of CPU architecture and performance metrics
- Familiarity with performance testing tools like 'stress'(optional)
Key Questions Answered
How does CPU utilization affect system latency?
As CPU utilization increases, system latency tends to rise, leading to performance degradation. The article illustrates that higher CPU usage can result in increased CPU time per request, indicating that maintaining lower utilization levels can enhance overall system efficiency.
What is the Turbo Boost effect and how does it impact performance?
The Turbo Boost effect refers to the increase in CPU frequency under low utilization, which enhances performance. However, as utilization rises, CPU frequencies decrease due to thermal and power limits, leading to slower response times.
What is the 'Golden Ratio' of CPU utilization?
The 'Golden Ratio' of CPU utilization is the optimal threshold where CPU usage is high enough to prevent resource waste but low enough to avoid significant performance degradation. Identifying this balance helps in efficient resource provisioning.
What issues arise with Hyper-Threading under high CPU utilization?
Hyper-Threading can lead to reduced performance when CPU utilization exceeds a certain threshold. Beyond this point, the Linux kernel cannot fully utilize both virtual cores, resulting in inefficiencies in workload processing.
Key Statistics & Figures
CPU time per request
Increases as CPU utilization rises
This trend was observed across different instance types during the experiments conducted.
Optimal CPU utilization threshold
Approximately 61% for less than 40% CPU time degradation
This threshold was identified as a balance between resource efficiency and performance.
Technologies & Tools
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Orchestration
Kubernetes
Used to host the Large Unicorn Collider (LUC) environment for performance testing.
Hardware
Intel Cpus
The experiments were conducted using various Intel CPU models to analyze performance characteristics.
Operating System
Linux
The Linux kernel manages CPU load distribution and Hyper-Threading functionalities.
Key Actionable Insights
1Monitor CPU utilization closely to maintain optimal performance levels.By keeping CPU utilization below critical thresholds, you can prevent latency spikes and ensure smoother operation of applications, especially in production environments.
2Utilize performance testing tools like 'stress' to simulate load and assess system behavior.This approach allows for a better understanding of how your systems react under various loads, helping to identify potential bottlenecks before they impact users.
3Adjust CPU C-states to enable Turbo Boost benefits effectively.Enabling C-states can optimize power usage and improve CPU performance, particularly under low utilization scenarios, leading to better overall system responsiveness.
Common Pitfalls
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Over-provisioning resources based on perceived performance needs.
This often occurs when higher CPU utilization leads to decreased performance, creating a false impression that more resources are necessary. Instead, identifying the optimal utilization threshold can prevent unnecessary resource expenditure.
Related Concepts
CPU Architecture
Performance Optimization Techniques
Resource Provisioning Strategies