Memory Command Selection Policy for Read Latency Reduction
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Solution Overview
Problem
Existing command selection policies in memory systems, such as FCFS and FRFCFS, fail to prioritize read commands effectively, leading to increased latency and delayed program execution due to timing constraints and lack of prioritization of read operations over write operations.
Innovation Solution
Implementing a command selection policy that prioritizes read commands over write commands, similar to a modified FRFCFS policy, by categorizing commands into priority queues based on their type and readiness, ensuring that read commands are executed before write commands, especially when read-after-write dependencies are detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If FCFS or FRFCFS command selection policies are used, then commands are executed in a simple sequential order, but read commands are not prioritized over write commands leading to increased latency
Solution Approach 1:
The command selection policy is segmented into multiple priority levels, with read commands placed in higher priority queues and write commands in lower priority queues. This segmentation allows the system to differentiate and prioritize read operations without requiring complete redesign of the command execution mechanism.
Solution Approach 2:
The patent changes the priority parameter of read commands relative to write commands. By assigning higher priority values to read commands and lower priority values to write commands, the system ensures that read operations are executed first when multiple commands are ready, thereby reducing read access latency.
2Productivity
If read commands are prioritized over write commands, then read latency is reduced, but system complexity increases due to multiple priority queues and categorization logic
Solution Approach 1:
The command selection policy dynamically adjusts command execution order based on real-time readiness status and priority levels. The system continuously monitors which commands are ready and selects from appropriate priority queues, allowing flexible adaptation to changing system conditions without fixed rigid scheduling.
Solution Approach 2:
The patent incorporates feedback mechanisms where the command selection policy continuously monitors command readiness status and execution progress. Based on this feedback, the system adjusts which commands to execute next, ensuring that prioritized read commands are executed when ready while maintaining overall system coordination.
3Reliability
If commands are executed without prioritization, then the command selection policy is simple, but read-after-write dependencies may cause deadlocks and delayed program execution
Solution Approach 1:
The system performs preliminary detection of read-after-write dependencies before command execution. By identifying such dependencies in advance and prioritizing the appropriate commands, the system prevents deadlocks from occurring rather than resolving them after they arise.
Solution Approach 2:
The command selection policy acts as an intermediary between command issuance and execution. It mediates the execution order by detecting dependencies and inserting appropriate prioritization logic, thereby preventing deadlocks without requiring changes to the underlying memory architecture or command protocols.
Data Source
AI summary
Apparatuses and methods related to command selection policy for electronic memory or storage are described. Commands to a memory controller may be prioritized based on a type of command, a timing of when one command was received relative to another command, a timing of when one command is ready to be issued to a memory device, or some combination of such factors. For instance, a memory controller may employ a first-ready, first-come, first-served (FRFCFS) policy in which certain types of commands (e.g., read commands) are prioritized over other types of commands (e.g., write commands). The policy may employ exceptions to such an FRFCFS policy based on dependencies or relationships among or between commands. An example can include inserting a command into a priority queue based on a category corresponding to respective commands, and iterating through a plurality of priority queues in order of priority to select a command to issue.