Distributed shared arrays: A distributed virtual machine with mobility support for reconfiguration

Abstract

Distributed Shared Arrays (DSA) is a distributed virtual machine that supports Java-compliant multithreaded programming with mobility support for system reconfiguration in distributed environments. The DSA programming model allows programmers to explicitly control data distribution so as to take advantage of the deep memory hierarchy, while relieving them from error-prone orchestration of communication and synchronization at run-time. The DSA system is developed as an integral component of mobility support middleware for Grid computing so that DSA-based virtual machines can be reconfigured to adapt to the varying resource supplies or demand over the course of a computation. The DSA runtime system also features a directorybased cache coherence protocol in support of replication of user-defined sharing granularity and a communication proxy mechanism for reducing network contention. System reconfiguration is achieved by a DSA service migration mechanism, which moves the DSA service and residing computational agents between physical servers for load balancing and fault resilience. We demonstrate the programmability of the model in a number of parallel applications and evaluate its performance by application benchmark programs, in particular, the impact of the coherence granularity and service migration overhead.

Migration decision for hybrid mobility in reconfigurable distributed virtual machines

“…The service migration overhead was H = 50, as 100 times greater than the initial scaled workload. It confirms to our measurements of the runtime overhead of service migration in M-DSA [4]. Fig.…”

“…In contrast, application-level distributed virtual machines can be tuned to become more efficient for specific applications, and it is much easier to migrate these lightweight services in a network. The Global Object Space in JESSICA2 [17], and the Distributed Shared Array [4] in Traveler [15] are such examples.…”

“…By serializing and transferring capsules between physical machines, a VM can resume running after migration. To support virtual machine reconfiguration in Traveler [15], we designed a mobile distributed shared array (M-DSA) [4], which supports the migration of a DSA service to a new physical server when the original one is overloaded or going to fail.…”

“…Service migration techniques have been incorporated into many recently proposed systems. Examples include a VM-based architecture for grid computing in [3], capsule in Collective [10], M-DSA [4] in Traveler [15].…”

“…MALD [2] is an example that uses mobile agents to balance the workload of distributed web servers. In [15,4], we proposed a resource brokerage infrastructure, which assigns task agents to a distributed shared array (DSA), an application-level distributed virtual machine. Load-balancing is achieved via the agent migration.…”