Interrupt Controller Preferred CPU Binding

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Solution Overview

Problem

In computer systems, particularly in multi-processor and virtualized environments, the existing methods for managing interrupts lead to significant performance degradation due to latency and inefficient handling, especially when the designated CPU becomes unavailable or when virtual CPUs compete for physical CPU cycles.

Innovation Solution

An interrupt controller binds interrupts to a preferred CPU based on predetermined binding, redirecting them to another available CPU if the preferred one is not available, using a processor monitor to determine the least busy CPU for optimal load balancing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If all interrupt occurrences are sent to a designated CPU, then the interrupt handler code is likely found in the CPU cache improving performance, but significant performance degradation occurs when the designated CPU becomes unavailable

Engineering Contradiction:

Improveinterrupt handling performanceVSAvoidinterrupt handling availability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces an interrupt controller as an intermediary between devices and CPUs. This controller maintains a binding between interrupt-generating devices and preferred CPUs, dynamically determining which CPU receives each interrupt based on availability and load conditions, thus resolving the contradiction between performance optimization and availability assurance

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If interrupts are sent to any CPU in a multi-processor system, then CPU availability is maintained, but the interrupt handler code bounces between CPUs causing performance degradation

Engineering Contradiction:

ImproveCPU availabilityVSAvoidinterrupt handling performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent establishes predetermined bindings between interrupt-generating devices and preferred CPUs before interrupts occur. The interrupt controller consults these pre-established bindings and current CPU availability status to make routing decisions, preventing the bounce effect by proactively selecting the most appropriate CPU based on cached code location and current load conditions

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If a virtual CPU is suspended to handle exceptions or system management functions, then the virtual CPU can perform necessary tasks, but interrupt servicing latency increases significantly

Engineering Contradiction:

Improvevirtual CPU task handlingVSAvoidinterrupt servicing latency

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The patent implements dynamic interrupt routing that adapts to the real-time state of virtual CPUs. The interrupt controller monitors whether a preferred virtual CPU is suspended or running, and dynamically redirects interrupts to alternative available virtual CPUs or physical CPUs, thereby maintaining low latency while allowing virtual CPUs to perform necessary suspended tasks

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8312195B2Managing interrupts using a preferred binding between a device generating interrupts and a CPU

Publication Date: 2012.11.13 RED HAT INC

AI summary

A method and system for binding interrupts to central processing units (CPUs). An interrupt controller receives an interrupt that is generated by a device coupled to the computer system. The interrupt controller identifies a preferred CPU associated with the device based on a predetermined binding. If the preferred CPU is currently available, the interrupt is sent to the preferred CPU. If the preferred CPU is not currently available, the interrupt is sent to another CPU in the computer system that is currently available.