Memory Subsystem Request Control via Buffer Feedback
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Solution Overview
Problem
In memory sub-systems, the backlog of requests in the back-end buffers can lead to increased latency, inefficiency, and potential saturation, as the front-end sends requests without restraint, causing the back-end buffers to become overwhelmed.
Innovation Solution
Implementing a control mechanism in the front-end of the memory sub-system that utilizes multiple thresholds to throttle the receipt of commands from the host system, thereby reducing the backlog in the back-end buffers by signaling to the host when to provide additional requests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the front-end sends requests without restraint, then the productivity of the memory sub-system is improved, but the back-end buffers become saturated and latency increases
Solution Approach 1:
The front-end controller continuously monitors the number of outstanding requests in the back-end buffers and uses this feedback to dynamically adjust request sending behavior. When the buffer depth exceeds a threshold, the controller throttles or pauses request transmission, preventing saturation while maintaining high throughput when buffers are healthy.
Solution Approach 2:
The request sending mechanism transitions from static (unrestrained) to dynamic control. The front-end controller adapts its request sending rate in real-time based on back-end buffer status, adjusting throughput dynamically to match actual system capacity and avoid latency-prone saturation.
2Productivity
If the front-end sends requests without restraint, then the productivity is improved, but the device complexity increases due to buffer management
Solution Approach 1:
The front-end controller autonomously manages buffer depth by monitoring outstanding requests and self-regulating request sending without external intervention. This self-service approach handles buffer control complexity internally, maintaining high throughput while avoiding the need for complex external buffer management systems.
3Reliability
If multiple thresholds are used to throttle requests, then the reliability of the memory sub-system is improved, but the device complexity increases
Solution Approach 1:
The buffer depth threshold is segmented into multiple levels (e.g., warning threshold and critical threshold). Each threshold triggers different throttling strategies, allowing granular control over request sending behavior. This segmentation improves reliability by providing staged protection against saturation while keeping the control logic modular and manageable.
Data Source
AI summary
A request can be provided, from a front-end of a memory sub-system, to a processing device of the memory sub-system and deleting the request from a buffer of the front-end of the memory sub-system. Responsive to deleting the request from the buffer, determining a first quantity of requests in the buffer and responsive to deleting the requests from the buffer, determining a second quantity of outstanding requests in the back-end of the memory sub-system. Responsive to deleting the request from the buffer and providing the request to the processing device, determining whether to provide a response to a host, wherein the response includes an indication of the quantity of requests in the buffer and of outstanding requests in a back-end of the memory sub-system, based on a comparison of the second quantity of outstanding requests to a threshold.