R. Veldema, B. Larsen, and M. Philipssen (Germany)
DSM, protocol, virtual machine.
A DSM protocol ensures that a thread can access data allo cated on another machine using some consistency protocol. The consistency protocol can either replicate the data and unify replica changes periodically or the thread, upon re mote access, can migrate to the machine that hosts the data and access the data there. There is a performance trade off between these extremes. Data replication suffers from a high memory overhead as every replicated object or page consumes memory on each machine. On the other hand, it is as bad to migrate threads upon each remote access since repeated accesses to the same distributed data set will cause repeated network communication whereas replication will incur this only once (at the cost of increased administration overhead to manage the replicas). We propose a hybrid protocol that uses selective repli cation with thread migration as its default. Even in the pres ence of extreme memory pressure and thread-migrations, our protocol reaches or exceeds the performance that can be achieved by means of manual replication and explicit changes of the application’s code.
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