Addressing moved modules in a capability-based distributed shared memory

The MONADS distributed shared memory (DSM) consists of a single, very large, paged virtual memory space distributed across an arbitrary number of discrete nodes connected to a network. Each node acts as a server for the virtual memory pages stored at that node. The key to transparent access to the pages of the modules stored in the DSM is the use of structured addresses containing embedded location information. There is a problem with allowing modules to be moved because the location information, embedded in the addresses used to access the data in them, does not describe the correct storage location. This paper reviews an initial solution to the problem of accessing pages from moved modules. The required sequence of operations represents a significant, and usually unnecessary system overhead, since most page retrievals involve locally stored pages. An alternate solution to the problem is presented. This solution allows most page accesses, both local or remote and from moved or unmoved modules, to occur without unnecessary overheads