Memory Image Capture via Persistent Memory Metadata
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Solution Overview
Problem
Current systems for capturing memory images are inefficient due to the need to copy volatile memory data into non-volatile storage, leading to prolonged processing times and resource usage, especially when dealing with large data sets, which impacts system performance and failure recovery times.
Innovation Solution
The technique employs persistent memory (PMEM) to store and manage memory images, allowing metadata representation of the memory state instead of copying data, thereby reducing the time and resources required for image capture, as PMEM is already in a persistent state and does not need to be copied to non-volatile storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If volatile memory data is copied into non-volatile storage for memory image capture, then the memory image is preserved, but the processing time and resource usage increase significantly
Solution Approach 1:
The patent uses copy-on-write metadata to represent memory images instead of copying actual memory data. When a memory region is allocated, a metadata entry is created that points to the physical memory location, allowing the system to track memory state without duplicating the underlying data, thus preserving memory images with minimal overhead
Solution Approach 2:
The patent changes the fundamental parameter of memory persistence by using persistent memory (PMEM) technology that maintains data without power, eliminating the need for active copying to non-volatile storage. The system transitions from volatile memory requiring continuous power and copying to PMEM that inherently preserves data state
2Reliability
If volatile memory data is copied into non-volatile storage for memory image capture, then the memory image is preserved, but the system resources and processing power are consumed
Solution Approach 1:
The patent replaces data copying with metadata copying. Instead of copying gigabytes of memory data to non-volatile storage, the system copies only the metadata structures (page tables, allocation information) that describe the memory state, reducing resource consumption by several orders of magnitude
Solution Approach 2:
The patent substitutes the mechanical process of data copying with a logical/metadata-based system. The copy-on-write metadata mechanism provides a logical representation of memory state without requiring physical data movement, replacing resource-intensive mechanical copying operations
3Reliability
If memory images are captured using traditional copying methods, then complete memory state is preserved, but the capture process is slow and impacts system performance
Solution Approach 1:
The patent uses copy-on-write metadata that can be captured and stored with minimal system impact. The metadata structure allows for efficient serialization and storage without requiring the memory capture process to stall or slow down system operations, maintaining productivity while preserving state
Data Source
AI summary
A memory image can be captured by generating metadata indicative of a state of volatile memory and/or byte-addressable PMEM at a particular time during execution of a process by an application. This memory image can be persisted without copying the in-memory data into a separate persistent storage by storing the metadata and safekeeping the in-memory data in the volatile memory and/or PMEM. Metadata associated with multiple time-evolved memory images captured can be stored and managed using a linked index scheme. A linked index scheme can be configured in various ways including a full index and a difference-only index. The memory images can be used for various purposes including suspending and later resuming execution of the application process, restoring a failed application to a previous point in time, cloning an application, and recovering an application process to a most recent state in an application log.