Opportunistic Garbage Collection in NAND Flash Memory
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Solution Overview
Problem
Current NAND flash memory management systems face challenges in efficiently performing garbage collection, particularly in multithreaded environments with real-time media requirements, due to the asynchronous and time-consuming nature of erase/write cycles, which can lead to significant latency and buffer requirements.
Innovation Solution
The system performs demand-driven opportunistic garbage collection by dividing operations into atomic read, write, and block erase phases, and utilizes idle periods indicated by the processor to execute these operations, allowing for proactive management of garbage collection without disrupting real-time media streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If garbage collection is performed using traditional erase/write cycles in NAND flash memory, then obsolete data can be removed and storage space can be reclaimed, but significant latency is introduced and real-time media streams are disrupted
Solution Approach 1:
The patent segments the traditional atomic erase/write cycle into separate read, write, and erase operations that can be executed independently and asynchronously. This allows the garbage collection process to be broken down into manageable tasks that can be interleaved with real-time media operations, reducing latency while maintaining garbage collection effectiveness
Solution Approach 2:
The patent implements preliminary actions by pre-reading data from blocks scheduled for erasure and pre-writing it to new locations before the actual erase operation begins. This preparation work is done in advance during idle periods, so that when erasure is needed, the data migration is already complete, reducing the critical path latency
2Reliability
If large latency buffers are used to accommodate asynchronous garbage collection operations, then real-time media streams can maintain continuous playback, but memory resources are consumed and system complexity increases
Solution Approach 1:
The patent enables the memory subsystem to service itself by implementing an idle period detection mechanism that automatically identifies when real-time media operations are not actively accessing memory. During these self-identified idle periods, the system autonomously performs garbage collection operations without requiring external intervention or large buffers, as the memory is naturally available
3Productivity
If garbage collection operations are performed during active media playback, then storage maintenance can occur continuously, but media playback latency increases and quality deteriorates
Solution Approach 1:
The patent implements periodic action by scheduling garbage collection operations to occur during naturally occurring idle periods between media playback events. Rather than attempting continuous maintenance that would interfere with playback, the system performs storage maintenance periodically when the media player is naturally paused or transitioning between operations, maintaining both playback quality and storage health
Data Source
AI summary
A method and system for performing garbage collection in a memory is disclosed. Aspects of the exemplary embodiment include dividing garbage collection into atomic operations, including read, write, and block erase; storing read cycle times, write cycle times, and block erase cycle times of the memory; receiving a communication from a processor indicating at least one idle period when an application executing on the processor will not make a request of the memory, wherein the communication indicates a time duration of the at least one idle period; and in response, performing at least one of the garbage collection atomic operations within the time duration, whereby garbage collection can be performed during the at least one idle period, rather than when the memory is substantially full.