A b+ tree management method based on remote direct non-volatile memory access

Abstract

The invention relates to a B+ tree management method based on remote direct non-volatile memory access. This method stores the internal nodes of the complete B+ tree on the DRAM. The volatile leaf nodes on the DRAM only contain keywords, and the corresponding data is stored in the leaf nodes on the non-volatile memory. Each volatile leaf node is associated with A non-volatile leaf node; the client obtains the remote lock through the RDMA atomic operation, and then sends the operation command of the B+ tree to the server; the server reserves the space for remote operation in the corresponding non-volatile leaf node, and then the client The remote write technology using RDMA uses logs to directly persist data to non-volatile leaf nodes on the server side. The present invention uses the client to cooperate with the server to operate the B+ tree based on non-volatile memory, which reduces the processing burden of the server in the case of concurrent access; in addition, the operation of the non-volatile leaf nodes in the form of a log alleviates the NVM of write wear.

Description

technical field [0001] The invention relates to a B+ tree management mechanism, in particular to a B+ tree management method based on remote direct non-volatile memory access. Background technique [0002] As an important part of the function of the storage system, the index can speed up the search of data. As an index structure of the widely used B-tree class, it is originally a balanced multi-way search tree designed for the access characteristics of disks. For a B-tree of order m, its main characteristics are: each node has at most m subtrees; except for the root node, other nodes have at least m / 2 (rounded) subtrees; the root node has at least two subtrees, Except that the B-tree contains only one node; all leaf nodes are on the same level; the data on all nodes is arranged in order by key. The size of the nodes of the B-tree is usually the same as the block size of the disk. In this way, each time an element is searched, a node to which it belongs is read and prefetch...

AI Technical Summary

Problems solved by technology

However, with the development of computer technology, the performance gap between memory and disk is getting bigger and bigger, and the performance of disk can no longer meet the needs of massive data analysis; data storage architecture has gradually centered on memory; and new storage devices, Such as PCM (Phase Change Random Access Memory) and 3D Xpoint, which have the characteristics of non-volatility of external memory, high integration and memory-level access speed, etc., which can make up for the volatile characteristics of existing DRAM (Dynamic Random Access Memory) , high energy consumption and limited capacity, the non-volatile memory (NVM, Non-Volatile Memory) based on these devices has become a hot spot for computer designers and researchers to improve the performance of storage systems

It is true that the design of the index structure for non-volatile memory also faces new challenges, such as non-volatile memory upgrading the original data persistence level from external memory to memory and its own write wear and other problems; generally speaking, memory The level of data persistence is to explicitly refresh the data in the CPU cache to the memory. For the B+ tree, due to the order of the elements on the leaf nodes, the insertion of the elements will cause the movement of the data, resulting in The overhead of a lot of CPU cache refreshing reduces the performance of the B+ tree; and in a multi-core system, the performance reduction of the single-threaded B+ tree operation will make it occupy the lock for too long, which will lead to more concurrent competition among multiple threads. Intense, further reducing the performance of the B+ tree and the utilization of system resources; the existing stand-alone can no longer meet the needs of large data storage, but in a distributed environment, because the processing of the B+ tree is server-centric, so The B+ tree design based on non-volatile memory faces the same challenges, such as the trade-off between data persistence and concurrency performance, and NVM write wear, etc.

Images