Storage Device Interrupt Generation Method
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Solution Overview
Problem
Flash memory devices, such as SSDs, experience performance overhead due to frequent interrupts, which occur when the difference between the tail and head pointers of a completion queue is not managed efficiently, leading to unnecessary interrupt generation and resource consumption.
Innovation Solution
A method and device for reducing interrupt generation frequency by issuing interrupts only when specific conditions are met, including a mismatch between tail and head pointers, exceeding an aggregation threshold, or elapsed time since the last interrupt, thereby optimizing the completion queue management and reducing resource consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If interrupts are generated for every completion entry in the completion queue, then the host equipment can process commands promptly, but the interrupt generation frequency increases causing performance overhead
Solution Approach 1:
Multiple completion entries are merged into a single interrupt notification. The storage device accumulates completion entries in the completion queue and generates one interrupt when the queue is full or a threshold is reached, rather than generating separate interrupts for each completion entry. This reduces interrupt frequency while ensuring all completed commands are notified.
Solution Approach 2:
The storage device uses periodic polling or threshold-based triggering to determine when to generate interrupts. Instead of continuous interrupt generation for every event, the system checks the completion queue at intervals or when specific conditions (such as queue fullness or time elapsed) are met, creating a periodic interrupt pattern that reduces overall interrupt frequency.
2Measurement precision
If the difference between tail pointer and head pointer is monitored continuously, then completion queue status is accurately tracked, but system overhead increases
Solution Approach 1:
The storage device calculates the difference between tail and head pointers in advance when determining whether to generate an interrupt. Instead of continuously monitoring the pointer difference, the system performs this calculation only when needed for interrupt decision-making, such as when the completion queue reaches a threshold or at periodic intervals, reducing unnecessary processing.
3Speed
If interrupts are issued frequently to ensure timely command completion notification, then command processing responsiveness is improved, but resource consumption increases
Solution Approach 1:
The system dynamically adjusts interrupt generation parameters such as the threshold for completing commands before triggering an interrupt and the time interval between interrupts. By changing these parameters based on system conditions, the device optimizes the balance between responsiveness and resource consumption, generating interrupts only when necessary rather than at fixed high frequency.
Data Source
AI summary
An interrupt generation method of a storage device includes executing a command provided by a host, writing a completion entry in a completion queue of the host upon completing execution of the command, and issuing an interrupt corresponding to the completion entry to the host in response to at least one of a first interrupt generation condition, a second interrupt generation condition, and a third interrupt generation condition being satisfied. The first interrupt generation condition is satisfied when a difference between a tail pointer and a head pointer of the completion queue is equal to a first mismatch value. The second interrupt generation condition is satisfied when the difference between the tail pointer and the head pointer is at least equal to an aggregation threshold. The third interrupt generation condition is satisfied when an amount of time that has elapsed since a previous interrupt was issued exceeds a reference time.