Host Memory Cache Tag Handling for Faster Memory System Start-Up
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Solution Overview
Problem
Existing memory systems face challenges in reducing start-up time due to the need for initializing cache tags, which limits the use of host bus bandwidth and prolongs system initialization.
Innovation Solution
Incorporation of a bitmap and cache tag initial value in the memory system to determine if cache tags have been accessed post-power supply, allowing the system to use initial values when necessary, thereby skipping unnecessary initialization during start-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cache tag initialization is performed during start-up, then cache reliability is ensured, but start-up time increases and host bus bandwidth is consumed
Solution Approach 1:
The patent stores initial values for cache tags in non-volatile memory before power-off. Upon power-on, the system checks a bitmap to determine which cache tags were accessed before power-off, and only initializes those specific tags rather than all cache tags, thereby reducing start-up time while ensuring reliability where needed
Solution Approach 2:
The patent applies different initialization strategies to different cache tags based on their access history stored in the bitmap. Accessed cache tags receive targeted initialization while unaccessed tags use pre-stored initial values, creating localized quality differences in the initialization approach
2Reliability
If cache tag initialization is performed during start-up, then cache data accuracy is ensured, but host bus bandwidth is consumed
Solution Approach 1:
The patent extracts only the necessary cache tags that were accessed before power-off (identified via bitmap) and initializes only those tags during start-up, rather than initializing the entire cache tag set, thereby reducing host bus bandwidth consumption while maintaining data accuracy for relevant entries
Solution Approach 2:
Initial values for cache tags are prepared and stored in advance in non-volatile memory. During start-up, the system retrieves these pre-prepared initial values for specific tags based on bitmap information, eliminating the need to transfer and initialize all cache tags through the host bus
Data Source
AI summary
A memory system is connectable to a host having a host memory and includes a non-volatile memory that stores management data, a memory controller configured to manage caching of parts of the management data in cache lines of the host memory, and a first memory configured to store a bitmap that includes a bit indicating whether the memory controller has accessed first data stored in the host memory after power was last supplied to the memory system. The first data indicates whether or not a part of the management data corresponding thereto is stored in one of the cache lines, and the memory controller is configured to perform either a first operation of reading the first data from the host memory or a second operation of reading an initial value of the first data managed by the memory controller, based on the bitmap.