Debug Buffer Management via Priority-Based Eviction in NVMe SSDs
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Solution Overview
Problem
The PCIe interface in NVMe SSDs faces bandwidth limitations, leading to decreased performance and increased latency when sideband information is loaded, which can result in irreproducible bugs and failure to debug issues due to bandwidth overload.
Innovation Solution
A data storage device with a controller that manages bandwidth by prioritizing debug information, removing old low-priority data from a debug buffer when new data lacks available entries, and distributing available bandwidth among tenants, ensuring critical debug information is transmitted without impacting user data performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If debug information is transmitted through the PCIe interface, then debug capability is improved, but PCIe interface performance deteriorates due to bandwidth limitation
Solution Approach 1:
The patent segments the interface functionality by separating user data transmission from sideband information transmission. The PCIe interface is divided into distinct channels: one for user data and another for sideband information including debug data. This segmentation allows debug information to be transmitted without competing for bandwidth with user data, thus maintaining PCIe interface performance while improving debug capability.
2Loss of information
If sideband information is loaded onto the PCIe interface, then debug information transmission is improved, but transfer latency increases due to bandwidth exhaustion
Solution Approach 1:
The patent introduces an intermediary mechanism - a dedicated sideband channel - that mediates between the need to transmit debug information and the requirement to maintain low transfer latency. This sideband channel acts as a separate pathway that does not interfere with the main user data transmission channel, thereby enabling debug information transmission without increasing transfer latency for user data.
3Adaptability or versatility
If the PCIe interface bandwidth is shared with management information, then device functionality is improved, but available bandwidth for debug information decreases
Solution Approach 1:
The patent applies segmentation by creating distinct bandwidth allocation zones within the PCIe interface. Management information, user data, and sideband information each occupy separate segments or channels. This allows the device to maintain full functionality by supporting multiple information types simultaneously without them competing for the same bandwidth resources, thus preserving available bandwidth for debug information while enhancing device functionality.
Data Source
AI summary
A data storage device includes a memory device and a controller coupled to the memory device. The controller is configured to receive new debug information, determine that a debug buffer does not have any available free entries for the new debug information, compare the priority information to a lowest priority information of old debug information stored in the debug buffer, remove a most recent old debug information that has a lowest priority information from the debug buffer, and place the new debug information and corresponding priority information in the debug buffer.