Книга: Distributed operating systems

9.6.3.The COOL Generic Runtime System

9.6.3.The COOL Generic Runtime System

The COOL generic runtime uses clusters and context spaces to manage objects. Objects are persistent and exist on disk when no process has them mapped in. Operations are provided to the language runtime system to create and delete objects, map them into and out of address spaces, and invoke their methods. When an object invokes a method of another object that is located in its own cluster, the invocation is done by a local procedure call. When the invoked object is in a different cluster, the generic runtime system is used to ask the COOL base to arrange for the remote invocation. Because the overhead of intracluster invocations is so much smaller than that of intercluster invocations, putting objects that invoke each other a lot together in one cluster greatly reduces system overhead. In COOL-1, all invocations were effectively intercluster operations, which proved to be expensive.

The generic runtime system has a standard interface to the language-dependent runtime systems that use it. The interface is based on up calls, in which the generic runtime system calls the language runtime system to find out properties of objects, for example, to find internal pointers for relocation purposes when an object is mapped in.

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