Multi-Level Time Decay Storage Queue for I/O Prioritization
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Solution Overview
Problem
Existing data storage systems face inefficiencies in I/O processing due to excessive CPU resource consumption and inconsistent I/O response times, particularly when handling multiple pending I/O operations with varying priorities and service level objectives, leading to potential SLO violations and decreased system performance.
Innovation Solution
Implementing a method that utilizes multiple queues for pending I/O operations, each with a Time to Expiry (TTE) and Remaining Credits (RC), where I/Os are routed based on their expected execution time (EET) and service level, allowing for dynamic shifting between queues to optimize execution and maintain consistent performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If multiple pending I/O queues are used to handle varying priorities and service levels, then I/O response time consistency is improved, but CPU resource consumption increases
Solution Approach 1:
The patent segments pending I/O operations into multiple priority-based queues (e.g., high priority, normal priority, low priority queues) with different Time to Expiry (TTE) values. Each queue handles I/Os with similar service level requirements, allowing the system to process time-critical I/Os faster while reducing CPU overhead by avoiding a single large queue that requires frequent full traversals.
Solution Approach 2:
The patent implements dynamic I/O shifting between queues based on aging mechanisms and TTE comparisons. As I/Os wait in lower-priority queues, their effective priority increases over time, and they are automatically shifted to higher-priority queues when appropriate. This dynamic adjustment ensures time-critical I/Os receive timely service without requiring constant CPU intervention to requeue all I/Os.
2Device complexity
If I/O operations are processed in a single queue without priority differentiation, then device complexity is reduced, but I/O response time consistency deteriorates
Solution Approach 1:
The patent divides the single I/O queue into multiple segmented queues organized by priority levels and TTE ranges. Each segment handles I/Os with specific service level requirements, enabling the system to meet diverse response time targets while maintaining manageable complexity through structured organization rather than a monolithic queue.
Solution Approach 2:
The patent introduces TTE (Time to Expiry) as a key parameter for queue selection and I/O shifting decisions. By comparing TTE values against current time and queue characteristics, the system dynamically determines optimal queue placement and shifting时机, achieving response time consistency through parameter-driven control rather than complex hierarchical structures.
3Loss of time
If I/O shifting between queues is performed frequently to optimize execution, then I/O response time consistency is improved, but processing overhead increases
Solution Approach 1:
The patent implements periodic I/O shifting at TTE boundaries rather than continuously monitoring and shifting I/Os at every moment. The system checks for I/O shifting opportunities at defined intervals (e.g., when TTE expires or at scheduled checkpoints), reducing processing overhead while still ensuring time-critical I/Os are moved to appropriate queues in a timely manner.
Solution Approach 2:
The patent uses TTE values and queue status feedback to intelligently determine when I/O shifting is necessary. The system monitors I/O aging, queue depths, and TTE comparisons to make shifting decisions only when beneficial, avoiding unnecessary shifting operations that would consume CPU resources without improving response time consistency.
Data Source
AI summary
Techniques for processing I/O operations may include: receiving an I/O having an associated expected execution time (EET) and I/O service level; selecting, in accordance with the EET and service level of the I/O, a first I/O queue from multiple pending I/O queues; inserting the I/O into the first I/O queue; and performing I/O shifting. I/O shifting may include shifting I/Os from one pending I/O queue to another that is ranked immediately higher than the one pending I/O queue. The multiple I/O queues may be ranked from a highest priority queue to a lowest priority queue. I/O shifting may shift I/Os from the highest priority queue to execution and shifting I/Os from another queue into the highest priority queue. I/O shifting is subject to remaining credits available of the multiple I/O queues and time distance between source and target queues.