Tapeworm: High-Level Abstractions of Shared Accesses

We describe the design and use of the tape mechanism, a new high-level abstraction of accesses to shared data for software DSMs. Tapes can be used to "record" shared accesses. These recordings can be used to predict future accesses. Tapes can be used to tailor data movement to application semantics. These data movement policies are layered on top of existing shared memory protocols.

We have used tapes to create the Tapeworm prefetching library. Tapeworm implements sophisticated record/replay mechanisms across barriers, augments locks with data movement semantics, and allows the use of producer-consumer segments, which move entire modified segments when any portion of the segment is accessed. We show that Tapeworm eliminates 85% of remote misses, reduces message traffic by 63%, and improves performance by an average of 29% for our application suite.