SCM Read Cache Queue Depth Threshold Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Computing devices face challenges in managing the latency and capacity of volatile cache memory, as it has lower latency but limited capacity and higher cost compared to non-volatile storage, and implementing storage class memory (SCM) read cache to extend volatile cache capacity while managing data rate thresholds to prevent increased latency.
Innovation Solution
A method is introduced where a controller determines a representative IO request latency and compares it to a latency threshold to manage the data rate with SCM read cache, adjusting queue depth thresholds to prevent exceeding the data rate threshold, thereby reducing high latency for IO requests by selectively using, dropping, or bypassing the SCM read cache.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If volatile cache memory is used to reduce latency, then access speed is improved, but capacity is limited and cost increases
Solution Approach 1:
The cache memory is segmented into multiple levels: volatile cache memory for high-speed access and SCM read cache for extended capacity. This segmentation allows the system to utilize both fast volatile memory and larger non-volatile storage, resolving the contradiction between speed and capacity by dividing the memory hierarchy into functional segments.
Solution Approach 2:
The SCM read cache is nested within the storage system architecture, acting as an intermediate layer between the volatile cache and the main storage. This nested structure enables the system to benefit from both the speed of volatile cache and the capacity of SCM, effectively nesting different memory types to overcome individual limitations.
2Quantity of substance
If SCM read cache is used to extend volatile cache capacity, then capacity is improved, but data rate threshold may be exceeded causing increased latency
Solution Approach 1:
The queue depth threshold for SCM read cache is made dynamic rather than static. The threshold adjusts based on current system conditions and data rate requirements, allowing the system to optimize between capacity utilization and latency performance. When latency concerns arise, the threshold can be reduced to limit data rate, and when capacity is needed, it can be increased.
Solution Approach 2:
The system implements feedback mechanisms to monitor the data rate and latency performance of the SCM read cache. Based on this feedback, the queue depth threshold is automatically adjusted to maintain optimal performance, preventing the data rate from exceeding thresholds that would cause increased latency while still utilizing the extended capacity.
3Productivity
If queue depth threshold for SCM read cache is increased to utilize capacity, then data rate is improved, but latency increases when threshold is exceeded
Solution Approach 1:
The queue depth threshold is implemented as a dynamic parameter that adapts to system conditions. When the system can handle higher data rates, the threshold is increased to maximize productivity. When latency becomes a concern, the threshold is automatically reduced, creating a dynamic balance between data rate and latency that resolves the contradiction.
Solution Approach 2:
The system changes the queue depth threshold parameter based on observed performance metrics. By monitoring data rate and latency, the system adjusts this critical parameter to maintain optimal operation, increasing it when productivity is the priority and decreasing it when latency must be minimized, thus resolving the contradiction between these two objectives.
Data Source
AI summary
Examples include storage class memory (SCM) queue depth threshold adjustment. Examples may adjust the SCM queue depth threshold of a controller based on whether an IO request latency threshold for an SCM read cache is exceeded. Examples may determine whether to process an IO request using the SCM read cache based on an SCM queue depth of the controller and the SCM queue depth threshold.