Memory Controller Speculative Reading for Limited Cache Capacity
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Solution Overview
Problem
Memory controllers with insufficient volatile memory capacity to cache the entire translation table experience deteriorated responsiveness due to frequent reading from nonvolatile flash memory, especially when logical addresses are noncontiguous and physical addresses are interspersed.
Innovation Solution
Implementing a speculative reading mode in the memory controller that predicts and reads data anticipated by the host, adaptively switching between normal and speculative modes based on contiguous physical address patterns, and caching data in volatile memory to reduce translation table reads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the memory controller uses only volatile memory to cache the translation table, then the access speed is fast, but the volatile memory capacity is insufficient to cache the whole translation table
Solution Approach 1:
The translation table is divided into multiple segments or pages that can be selectively loaded into volatile memory. The memory controller caches only the necessary portions of the translation table in volatile memory while keeping the rest in nonvolatile flash memory, thus resolving the contradiction between limited volatile memory capacity and the need for fast access.
Solution Approach 2:
The memory controller performs preliminary reading of translation table data from flash memory into volatile memory based on predicted access patterns. By anticipating which translation table entries will be needed soon and loading them in advance, the system prepares data before actual access occurs, improving speed without requiring entire translation table to be cached.
2Quantity of substance
If the memory controller reads the translation table from flash memory as necessary, then the volatile memory capacity constraint is satisfied, but the responsiveness to host access deteriorates
Solution Approach 1:
The memory controller reads translation table data from flash memory in advance based on predicted host access patterns. By anticipating which translation entries will be needed and loading them into volatile memory before actual host access occurs, the system eliminates wait time during actual access operations, thus improving responsiveness while still using limited volatile memory capacity.
Solution Approach 2:
The memory controller monitors host access patterns and uses this feedback information to dynamically adjust which translation table segments are loaded into volatile memory. By continuously adapting the cached translation table portions based on actual usage patterns, the system optimizes responsiveness for the specific workload while efficiently utilizing limited volatile memory resources.
3Adaptability or versatility
If the logical addresses are noncontiguous and physical addresses are interspersed, then the data is stored in flash memory according to translation mapping, but the reading efficiency decreases due to noncontiguous access patterns
Solution Approach 1:
The memory controller merges multiple noncontiguous physical address accesses into a single contiguous read operation from flash memory. By combining several scattered translation table entries that need to be accessed into one continuous read sequence, the system maintains the flexible translation mapping capability while significantly improving reading efficiency by eliminating the overhead of multiple separate access operations.
Data Source
AI summary
According to one embodiment, a memory controller has a speculative reading mode of reading in advance data predicted to be requested by the host from a nonvolatile memory. The memory controller records a physical address of the nonvolatile memory at which data that is last requested to be read by the host is stored, when the host requests data to be read, determines whether to transition to the speculative reading mode, based on a physical address of the nonvolatile memory at which the requested data is stored and the recorded physical address, and when transition to the speculative reading mode, read, from the nonvolatile memory, data in a range determined with respect to a physical address associated with a logical address specified by the host.