A GPU Multiversion B-Tree

We introduce a GPU B-Tree that supports snapshots and offers updates, point queries, and linearizable multipoint queries. The supported operations can be performed in a phase-concurrent, asynchronous, or fully-concurrent fashion. Our B-Tree uses cacheline-sized nodes linked together to form a version list and a GPU epoch-based reclamation scheme to reclaim older nodes' versions safely. Our data structure supports snapshots with minimal overhead in point queries (1.04x slower) and insertions (1.11x slower) versus a B-Tree that does not support versioning. Our linearizable B-Tree performs similarly to the non-linearizable baseline for read-heavy workloads and 2.39x slower for write-heavy workloads when performing concurrent range queries and insertions. In addition, we introduce different GPU-aware snapshot scopes that allow the use of our data structure for phase-concurrent (synchronous), stream-concurrent (asynchronous), and on-device fully-concurrent operations.