Distributed Shared Memory

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In a DSM system, the address space is divided up into pages, with the pages being spread over all the nodes in the system.

When a CPU references an address that is not local, a trap occurs, and the DSM software fetches the page containing the address and restarts the faulting instruction, which now completes successfully.

Replication:

To enhance performance, we can replicate pages that are read only. So we can have a copy for the second CPU without the original CPU memory being invalidated or disturbed.

Also read-write can have replication but if a replicated page is suddenly modified, special action has to be taken to prevent having multiple, inconsistent copies in existence.

How big the chunk should be ? Big

Advantages: The startup time for a network transfer is fairly substantial, it does not really take much longer to transfer 4096 bytes than it does for 1024 bytes.

Disadvantages: Network will be tied up longer and we can have false sharing.

False sharing; The transferred page has two unrelated variables, each is needed by a remote process, which means they will constantly traveling back and forth between the two machines.