Dynamic Virtual CPU Allocation for Interrupt Latency
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Solution Overview
Problem
Traditional CPU folding mechanisms in virtualized environments face challenges in balancing reduced interrupt service latency with the need to minimize the number of virtual CPUs, especially in interrupt-heavy environments, as they use algorithms with longer periodicity that are not aligned with the requirements for efficient interrupt processing.
Innovation Solution
The approach involves dynamically retrieving the time spent processing interrupts for a selected partition and comparing it to threshold values, increasing the number of virtual CPUs if the time exceeds the threshold, thereby optimizing interrupt processing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If CPU folding mechanisms are used to reduce the number of virtual CPUs, then context-switch overhead and lock contention are reduced, but interrupt service latency increases
Solution Approach 1:
The patent implements dynamic virtual CPU allocation that adapts to interrupt workload conditions. The system monitors interrupt handling metrics and dynamically adjusts the number of active virtual CPUs in response to changing workloads, allowing the system to optimize between context-switch overhead and interrupt service latency based on real-time conditions rather than using a fixed number of vCPUs
Solution Approach 2:
The patent changes the parameter of virtual CPU allocation from a static configuration to a dynamic parameter that responds to workload conditions. By monitoring interrupt handling metrics such as interrupt service latency and context-switch overhead, the system adjusts the number of active virtual CPUs as a variable parameter to optimize performance under different conditions
2Loss of time
If the number of virtual CPUs is increased to reduce interrupt service latency, then processing capacity is improved, but context-switch overhead and lock contention increase
Solution Approach 1:
The system dynamically adjusts the number of active virtual CPUs based on monitored interrupt workload conditions. When interrupt service latency increases, the system activates additional virtual CPUs to handle interrupts in parallel. When the workload decreases and context-switch overhead becomes significant, the system deactivates excess virtual CPUs, thus dynamically optimizing the balance between latency reduction and overhead minimization
3Stability of the object's composition
If traditional CPU folding algorithms with longer periodicity are used, then system stability is maintained, but interrupt processing requirements are not met
Solution Approach 1:
The patent implements periodic monitoring of interrupt handling metrics at appropriate intervals to detect when virtual CPU allocation needs adjustment. This periodic action allows the system to maintain stability by using structured monitoring intervals while achieving productivity improvements by responding to interrupt workload conditions in a timely manner through defined check cycles
Data Source
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AI summary
An approach is provided that retrieves a time spent value corresponding to a selected partition that is selected from a group of partitions included in a virtualized environment running on a computer system. The virtualized environment is provided by a Hypervisor. The time spent value corresponds to an amount of time the selected partition has spent processing interrupts. A number of virtual CPUs have been assigned to the selected partition. The time spent value (e.g., a percentage of the time that the selected partition spends processing interrupts) is compared to one or more interrupt threshold values. If the comparison reveals that the time that the partition is spending processing interrupts exceeds a threshold, then the number of virtual CPUs assigned to the selected partition is increased.