Hardware FIFO Buffer for Message Pointer Ordering in Storage Controllers
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Solution Overview
Problem
Flash storage devices face inefficiencies due to race conditions where message pointers are stored before associated messages, leading to incorrect data operations, and existing solutions like memory barriers and proxy blocks stall processors or increase latency.
Innovation Solution
Implementing hardware in the back-end processor to route order-sensitive transactions, such as messages and message pointers, through separate paths and using a FIFO buffer to ensure messages are stored before message pointers, preventing out-of-order processing and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate routing paths are implemented for order-sensitive and order-insensitive transactions, then message ordering reliability is improved, but device complexity increases
Solution Approach 1:
The patent divides the transaction routing into separate paths: order-sensitive transactions (messages and message pointers) are routed through a first path with FIFO buffering to ensure ordering, while order-insensitive transactions use a second path without buffering. This segmentation resolves the contradiction by implementing ordering guarantees only where needed, rather than applying complex ordering mechanisms to all transactions uniformly.
Solution Approach 2:
Different quality levels of service are applied locally to different transaction types. Order-sensitive transactions receive enhanced ordering guarantees through FIFO buffering and controlled delivery, while order-insensitive transactions receive standard delivery. This local differentiation allows the system to achieve high reliability for critical operations without unnecessarily complicating the entire system.
2Reliability
If FIFO buffer is used to ensure message delivery before message pointer, then transaction ordering is improved, but transaction latency increases
Solution Approach 1:
The patent segments transactions into order-sensitive and order-insensitive categories, applying FIFO buffering only to order-sensitive transactions. This selective buffering minimizes latency impact by preventing the buffering overhead from affecting order-insensitive transactions, while still ensuring correct ordering where required.
Solution Approach 2:
A FIFO buffer is introduced as an intermediary component between the processor and memory for order-sensitive transactions. This buffer receives transactions in order, stores them temporarily, and delivers them to memory in the correct sequence, preventing race conditions without requiring the processor to stall or wait for each transaction to complete before issuing the next one.
3Reliability
If memory barriers are used to prevent race conditions, then message ordering reliability is improved, but processor performance deteriorates due to stalling
Solution Approach 1:
The patent replaces the software-based memory barrier mechanism with a hardware-based FIFO buffer routing solution. Instead of using processor instructions that cause stalling and performance penalties, the system uses dedicated hardware routing paths with buffering to ensure message ordering. This substitution eliminates the need for processor stalling while maintaining reliability.
Solution Approach 2:
The FIFO buffer acts as an intermediary that decouples the message issuance from message delivery to memory. This allows the processor to continue issuing messages without waiting for memory delivery completion, eliminating the stalling effect of memory barriers while ensuring correct ordering through the buffered delivery mechanism.
4Reliability
If proxy block is used to ensure correct message storage, then ordering reliability is improved, but system complexity and latency increase
Solution Approach 1:
The patent extracts the ordering guarantee function from a complex proxy block system and implements it through simpler hardware routing with FIFO buffering. By removing the need for proxy block software/firmware layers and replacing them with dedicated hardware paths, the system achieves ordering reliability with reduced complexity.
Solution Approach 2:
The patent substitutes the complex proxy block mechanism with simpler hardware-based FIFO buffering and routing. This replacement eliminates the need for sophisticated software or firmware proxy block implementations, reducing system complexity while maintaining the essential ordering guarantee function.
Data Source
AI summary
Aspects of a storage device are provided that allows a controller to prevent message pointers from being stored in controller memory prior to associated messages due to race conditions, bus arbitration, or similar circumstances. The storage device may include hardware that routes order-sensitive transactions including messages to a first memory and order-sensitive transactions including message pointers to a second memory. The messages and message pointers may be provided from a first processor of the controller to a second processor of the controller. The hardware may hold delivery of each message pointer to the second memory until a delivery acknowledgement of an associated message is received from the first memory. The hardware may also route order-insensitive transactions including other instructions to a third memory different than the first and second memories without holding delivery. As a result, order-sensitive transactions may processed in the order received, without delaying processing of order-insensitive transactions.