Flash Memory Page Replacement Time Reduction

Solution Overview

Problem

Existing demand paging techniques do not effectively consider the characteristics of nonvolatile storage devices like flash memory, leading to inefficient page replacement times due to unnecessary operations and lack of hardware support for optimal algorithms.

Innovation Solution

A method and apparatus that reduce page replacement time by optimizing operations during data loading from flash memory, including independent operations during the busy state and updating memory mapping tables or invalidating caches, while using algorithms like the clock or Mach 2.5 algorithms to select replacement pages within a limited time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If the page fault handler waits for data to be read from the nonvolatile storage device before performing page replacement operations, then the operations can be performed in sequence with proper data availability, but the page replacement time increases due to sequential processing

Engineering Contradiction:

Improvepage replacement timeVSAvoiddata loading speed

Core Design Contradiction:

Loss of timeVSProductivity

Solution Approach 1:

The patent applies preliminary action by performing page replacement operations (selecting replacement pages, updating memory mapping tables, invalidating caches) before the data is actually loaded from the nonvolatile storage device. The page fault handler executes these operations during the device's busy state, preparing the memory system in advance so that when data loading completes, the page replacement is already finalized, thus reducing overall page replacement time.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the page fault handler performs multiple operations (reading data, securing memory space, updating mapping tables) in sequence, then each operation can be completed thoroughly, but the total processing time increases

Engineering Contradiction:

Improvepage replacement completenessVSAvoiddemand paging processing time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements continuity of useful action by overlapping the execution of multiple page replacement operations with the data loading process. Instead of waiting for data to be loaded before performing operations, the handler continuously executes page selection, memory mapping updates, and cache invalidation during the loading period, maximizing system utilization and reducing idle time while maintaining operational completeness.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent applies preliminary action by performing page replacement operations (selecting replacement pages, updating memory mapping tables, invalidating caches) before the data is actually loaded from the nonvolatile storage device. The page fault handler executes these operations during the device's busy state, preparing the memory system in advance so that when data loading completes, the page replacement is already finalized, thus reducing overall page replacement time.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If the system uses traditional demand paging algorithms without considering flash memory characteristics, then the algorithm can be implemented with existing hardware, but the page replacement efficiency decreases due to unnecessary operations

Engineering Contradiction:

Improvealgorithm implementation feasibilityVSAvoidpage replacement efficiency

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent applies parameter changes by modifying the operational parameters of the page replacement algorithm to match flash memory characteristics. Specifically, it changes the timing parameters to allow operations during the device's busy state, and adjusts the operational sequence to perform page replacement tasks in parallel with data loading, thereby optimizing efficiency without requiring hardware changes.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7953953B2Method and apparatus for reducing page replacement time in system using demand paging technique

Publication Date: 2011.05.31 SAMSUNG ELECTRONICS CO LTD

AI summary

A method and apparatus for reducing a page replacement time in a system using a demand paging technique are provided. The apparatus includes a memory management unit which transmits a signal indicating that a page fault occurs, a device driver which reads a page having the page fault from a nonvolatile memory, and a page fault handler that searches and secures a space for storing the page having the page fault in a memory. The searching and securing of the space in the memory is performed within a limited time calculated beforehand and a part of data to be loaded to the memory of the system is stored in the nonvolatile memory.