A Case for Dynamic Page Migration in Multiple-Writer Software DSM Systems

Software DSMs (SDSMs) are an appealing alternative to message passing, since they facilitate the programmability of clusters. However the ease of programming comes at the expense of performance. Although accesses of data that reside to the memory of remote nodes are transparent to the programmer, they suffer from significantly higher latencies compared to local accesses. As a consequence, it is desirable to move data as close as possible to the nodes that need them most. In this paper we introduce a protocol for dynamically migrating memory pages in home-based SDSM systems. In these systems each page has a designated home node; yet our protocol allows a node that heavily modifies a page to become its new home. The new protocol targets multiple-writer DSMs, i.e. DSMs that allow multiple nodes to concurrently modify the same page. The process is dynamic and transparent to the applications programmer. Moreover, it does not assume a specific consistency protocol. Experimental results show that our page migration protocol reduces remote page modifications, decreases the average memory access latency, as well as the overhead for the preservation of memory consistency. The benefit for the end-user is a significant improvement in application performance