External Adapter Direct I/O Interruption Initiation
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Solution Overview
Problem
In processing environments, especially those based on z/Architecture, external adapters face inefficiencies in initiating I/O interruptions due to the need for firmware processing and Alert attention, which can lead to race conditions and arbitration issues among multiple processors.
Innovation Solution
An external adapter can directly initiate I/O interruptions by sending requests to a system controller, which builds and broadcasts commands to processors to set pending interruption indicators in hardware arrays, eliminating the need for firmware processing and using a Filter Pending Interruption Array to manage and filter these requests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external adapters use firmware processing to initiate I/O interruptions, then the system maintains centralized control and coordination, but the processing time increases and system efficiency decreases
Solution Approach 1:
The patent extracts the interruption initiation function from the firmware layer and places it directly in the adapter hardware. The adapter can now directly set the initiative in the Interruption Queue Header and broadcast commands to processors without firmware intervention, eliminating the time-consuming firmware processing step while maintaining system control through the existing interruption arbitration mechanism.
Solution Approach 2:
The patent implements preliminary action by allowing the adapter to pre-set the interruption initiative and directly configure the interruption state before processor arbitration occurs. The adapter can set the initiative bit and prepare the interruption queue header in advance, so that when the interruption occurs, processors can immediately arbitrate without waiting for firmware processing.
2Productivity
If multiple processors are enabled for the same I/O interruption, then the system achieves load balancing and distribution, but race conditions and arbitration complexity increase
Solution Approach 1:
The patent uses the Interruption Queue Header and its associated lock mechanism as an intermediary that mediates access between multiple processors and the interruption state. The lock provides a standardized interface that simplifies the arbitration process, allowing multiple processors to safely compete for interruption handling without direct complex inter-processor coordination.
Solution Approach 2:
The patent replaces complex software-based arbitration mechanisms with hardware-level atomic operations and lock-based synchronization. The lock mechanism provides hardware-enforced mutual exclusion, substituting complex software arbitration logic with simpler, more reliable hardware-level control that reduces the overall system complexity despite multiple enabled processors.
3Reliability
If firmware processes Alert attention to determine initiative setting, then the system maintains centralized control logic, but the device complexity and processing overhead increase
Solution Approach 1:
The patent implements self-service by enabling the adapter to autonomously initiate and configure I/O interruptions without firmware assistance. The adapter can directly set the initiative, modify the Interruption Queue Header, and broadcast commands to processors, making the interruption initiation process self-contained at the hardware level and eliminating firmware complexity.
Solution Approach 2:
The patent extracts the control logic for interruption initiation from the firmware layer and relocates it to the adapter hardware layer. This separation removes the need for firmware to process Alert attention and determine initiative setting, simplifying the firmware while maintaining control logic in the hardware that directly manages the interruption state.
Data Source
AI summary
The setting of interruption initiatives is directly initiated by external adapters. An adapter external to the processors at which the initiative is to be made pending sends a request directly to a system controller coupled to the adapter and the processors. The system controller then broadcasts a command to the processors instructing the processors to set the interruption initiative.