An Evaluation of State Sharing Techniques in Distributed Operating Systems

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John, Ranjit
Ahamad, Mustaque
Ramachandran, Umakishore
Ananthanarayanan, R. (Rajagopal)
Mohindra, Ajay
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A shared memory abstraction in distributed systems (DSM) provides
ease of programming but could be costly to implement. Many protocols
have been proposed recently that are based on different approaches
for exploiting program semantics. We have implemented four different
protocols that embody the different memory semantics and have evaluated
them using applications that capture a wide range of state sharing
patterns. Our main goal is to quantify the relative performance of these
protocols with respect to representative applications. We expect the
results of such a study to be useful for an operating system designer to
choose the right protocol to support the DSM abstraction. One of the
surprising results is that memory systems that provide weaker consistency
or use synchronization information in coherence maintenance (e.g. release
consistency) do not provide significantly better performance than the basic
invalidation based protocol.
The disparity between the performance using these protocols and programmer
controlled state sharing can range from being insignificant to as high as
50% depending on application characteristics. The use of synchronization
information in conjunction with user directives will bridge this performance
gap but may decrease the programming ease of DSM.