Latency-Tolerant Software Distributed Shared Memory.

We present Grappa, a modern take on software distributed shared memory (DSM) for in-memory data-intensive applications. Grappa enables users to program a cluster as if it were a single, large, non-uniform memory access (NUMA) machine. Performance scales up even for applications that have poor locality and input-dependent load distribution. Grappa addresses deficiencies of previous DSM systems by exploiting application parallelism, trading off latency for throughput. We evaluate Grappa with an in-memory MapReduce framework (10× faster than Spark [74]); a vertex-centric framework inspired by GraphLab (1.33× faster than native GraphLab [48]); and a relational query execution engine (12.5× faster than Shark [31]). All these frameworks required only 60-690 lines of Grappa code.