Memory Controller Unmarked Extent List for Rollback Latency
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Solution Overview
Problem
Traditional methods for performing memory rollback operations in shared memory systems are inefficient, especially for large memory extents, as they require lengthy marking operations to determine which memory lines are participating in the rollback, leading to increased latency and reduced performance.
Innovation Solution
A method is introduced where a memory controller maintains a list of unmarked extents, allowing for quick determination of memory lines participating in enhanced memory operations, with background marking of large extents to avoid burdening the primary operation, and using meta state bits to track participation in memory rollback operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional marking operations are used to determine memory lines participating in rollback, then completeness of tracking is improved, but operation duration increases
Solution Approach 1:
The system performs preliminary actions by maintaining a pre-configured list of unmarked extents and using background marking to advance the marking process before rollback operations are needed. This allows the critical path rollback operation to proceed quickly while marking continues in the background, resolving the contradiction between complete tracking and fast operation.
Solution Approach 2:
The marking operation is segmented into critical path marking (performed immediately before rollback) and background marking (performed asynchronously in the background). This segmentation allows the system to maintain tracking completeness while reducing the duration of the critical rollback operation by offloading non-critical marking tasks to the background.
2Duration of action of moving object
If background marking is used for large extents, then marking operation duration is reduced, but system complexity increases
Solution Approach 1:
The system introduces an intermediary background marking mechanism that operates asynchronously between the main rollback operation and the memory extent marking. This intermediary process manages the complexity by handling marking tasks in the background while the primary rollback operation remains simple and fast, resolving the contradiction between reduced duration and increased complexity.
3Measurement precision
If traditional marking methods are used, then accuracy of memory line identification is improved, but productivity decreases
Solution Approach 1:
The system performs preliminary configuration of the unmarked extents list and uses background marking to pre-advance the marking process. This preliminary action ensures that when rollback operations need to identify memory lines, the critical path marking is already prepared or in progress, maintaining identification accuracy while improving overall rollback throughput.
Solution Approach 2:
The identification process is segmented into critical path identification (using pre-configured unmarked extents list for immediate accuracy) and background identification (continuing marking in the background). This segmentation maintains measurement precision for active rollback operations while improving productivity by parallelizing the identification work.
Data Source
AI summary
Disclosed in some examples are methods, systems, memory devices, and machine-readable mediums that allow a memory device to efficiently mark memory extents involved in an enhanced memory operation. An extent is marked if a meta state associated with the extent indicates that the extent is included in the enhanced memory operation. The largest memory extents of the operation are maintained in the memory device as a list of unmarked extents. When a primitive memory operation is received, the memory address is compared to the unmarked extents in the list to the meta state for that memory line. If the address is covered by the list of extents, or that line's meta state is marked, then the memory operation is performed including the enhanced memory operation.