Interrupt Request Segmentation for CPU Unplug Latency
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Solution Overview
Problem
Current methods for managing interrupt requests in computer systems are inefficient, particularly when a CPU is about to unplug, as they require searching through the entire interrupt list, leading to increased latency and resource waste, especially as the number of unplugged CPUs increases.
Innovation Solution
A method that categorizes interrupt requests into three groups: those that can be serviced by any CPU, those specific to a particular CPU, and those that need migration, creating a list for each CPU with identified migration candidates based on affinity, and efficiently migrating only the third group to a plugged CPU when an unplugging event occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system searches through the entire interrupt list to find interrupts targeted to a CPU about to unplug, then all interrupts can be found, but the migration latency increases and system resources are wasted
Solution Approach 1:
The interrupt list is segmented into three distinct groups: interrupts that can be serviced by any CPU, interrupts specific to a particular CPU, and interrupts that need migration. This segmentation allows the system to process only the relevant third group during migration, avoiding unnecessary search through the entire interrupt list and reducing latency while maintaining completeness.
Solution Approach 2:
The system performs preliminary categorization of interrupts into the three groups before the unplugging event occurs. By pre-identifying which interrupts need migration and creating a dedicated list for them, the system prepares the necessary information in advance, so that when unplugging happens, only the pre-identified interrupts need to be migrated, significantly reducing migration time.
2Reliability
If the system searches through the entire interrupt list for migration, then all interrupts are considered, but resource consumption increases especially as the number of unplugged CPUs increases
Solution Approach 1:
The interrupt list is divided into three segments, and the system only processes the third segment (interrupts needing migration) during the unplugging operation. This segmentation dramatically reduces the number of interrupts that require processing, lowering resource consumption while maintaining accurate migration of only the necessary interrupts.
Solution Approach 2:
The system performs preliminary sorting and categorization of interrupts into the three groups before the unplugging event. This pre-processing identifies and isolates the interrupts that need migration, creating a focused list that requires minimal processing resources during the actual migration operation, thereby reducing overall resource consumption.
3Reliability
If the system migrates all interrupts from a CPU about to unplug, then all interrupts are handled, but the complexity of the migration process increases
Solution Approach 1:
The migration process is simplified by segmenting interrupts into three categories and only processing the third category (interrupts needing migration). This segmentation reduces the complexity of the migration process from handling all interrupts to handling only a specific subset, making the process more manageable and less complex while maintaining completeness for the necessary interrupts.
Solution Approach 2:
The system performs preliminary categorization of interrupts into the three groups before migration is needed. This pre-organization simplifies the actual migration process by providing a pre-sorted list of only the interrupts that need to be migrated, eliminating the complexity of filtering and searching through the entire interrupt list during the migration operation.
Data Source
AI summary
Systems, methods, and computer readable medium are provided that improve the management of interrupt requests in multiple processor computer systems. Interrupt requests can be classified into three categories and the structure of the categories provide for specifying a list that needs to be migrated. The list can contain only those interrupt requests that can be handled by some of the processors that will never unplug or based on affinity. When a processor is about to unplug, the computer system can migrate that list. The system can also manage the other interrupt requests.