Generalized Optional Locking in Distributed Systems

T. Schöbel-Theuer (Germany)


Distributed Locking, Distributed Shared Memory, DSM, Distributed Algorithms


We present optional locking as a method for significantly speeding up distributed locks, and we generalize it to mul tiple lock types obeying a conflict relation. The generalized version can simulate the message passing paradigm on top of Distributed Shared Memory (DSM) with no more mes sages than explicit message passing would need. Thus we argue that message passing can be viewed as a true spe cial case of optional locking. As a consequence, the attrac tiveness of DSM programming models should increase sig nificantly due to well-recognized advantages such as sim plicity and reduced software engineering cost; mixtures of both message passing and shared data access patterns can be treated uniformly. Measurements and simulations based on database benchmarks indicate a substantial performance improvement of optional locking over conventional locking even in presence of multiple lock types.

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