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Selection of Workstations

All workstations, that participate in remote memory paging are registered in a common file. These workstations are known as remote memory servers, while the workstations that run applications that use remote memory for swapping are called clients. Depending on its workload, a workstation may act either as a server, or as a client.

All server workstations run a remote memory server that handles requests for pageins, pageouts, as well as for swap space allocation. When a client wants to swap out memory it picks the most promising server, asks for a number of page frames and starts sending requests to it. When a server runs out of memory, it denies further swap space allocation requests. When native memory-demanding processes start on a server workstation, part of the server's memory is swapped out to disk. Future requests will be serviced from the disk, and a note will be sent to the client, advising it to send no more pages to this server. On reception of this message, the client will try to find another server having enough free memory and migrate the pages that were stored by the loaded server to the new one. If no server having enough free memory can be found the client's local disk will be used to house these pages. Whenever the client's local disk is used to store some of it's paged out pages, the client periodically checks the memory load of all possible remote memory servers. If a server having enough free memory is found, some of the pages stored at the local disk are replicated to this server. Future requests concerning these pages will be served by the remote memory server rather than the disk.

Evangelos Markatos
Wed Aug 7 11:36:29 EET DST 1996