virtual memory 4513

science center had ported apl-360 to cms-apl. apl-360 had basicly its own subsystem monitor, terminal handler, swapper, storage manager etc ... running "real memory" under os-360. typical apl-360 workspaces were 16kbytes to 32kbytes.

in the move to cms-apl ... got rid of the subsystem monitor, terminal handler, swapper, etc ... as part of the apl implementation (allowing it to rely on the underlying infrastructure provided by cp67).

one of the things that the move to cms-apl environment was transition from 16kbyte ("real") workspaces to possibly multi-megabyte virtual memory workspaces. this created a big problem for the apl storage manager. it basically started with all unused space as available, then on ever buttignment, it allocated the next available unused space (discarding any old location containing a value). when it had exhausted unused space, it did garbage collection, compacting all "used" storage ... and creating a large contiguous area of unused space ... and then started all over again.

in a small, swapped, real-storage implementation, the side-effects of this strategy wasn't particularly bad. however, with very large virtual memory workspaces ... this strategy quickly touched all available virtual pages, then garbage collect-compact, and started all over.

the early vs-repack technology: D. Hatfield & J. Gerald, Program Restructuring for Virtual Memory, IBM Systems Journal, v10n3, 1971

was used to analyze this behavior and perfect a modified garbage collection implementation that was significantly more virtual memory friendly.

misc. past posts mentioning apl &-or hone

hone started out was a joint project with the science center and the marketing division to provide online, interactive support for all the sales, marketing, and field people ... initially with cp67 and later moved to vm370 base. a majority of the applications for the sales and marketing people were implemented in apl.

in the mid-70s, the various hone us datacenters were consolidated in northern cal. by the late 70s, the size of the defined US hone users was approaching 40k. in addition there were numerous clones of the US hone datacenter at various locations around the world. in the very early 80s, the high-available, fall-over hone implementation in northern cal. was replicated first with a new datacenter in dallas and then a 3rd datacenter in boulder (providing load balancing and fall-over across the datacenters in case of a natural disaster in cal.).

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