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[ih] vm vs. memory

Joe Touch wrote:
> IMO, they?re no more a stop-gap to networking than VM is to memory.
> But we?re digressing from the original thread...

that's hard to say, but i've forked the thread anyway.

vm is an example of something that started as a workaround but 
introduced us to a whole different way of thinking about memory. we now 
have systems in production that always have physical RAM enough for 
their work load, and who have no backing store for RAM (paging or 
swapping) but which still depend on virtual memory for other reasons:

1. linear address space; all processes think they have addresses 
starting from 0.

2. page-level protection; various parts of memory are only readable, or 
writable, or executable, when needed, and at certain privilege levels.

3. occasional sharing and/or persistence (memory mapped files).

4. occasional distributed persistence (networked virtual memory).

i think a lot of things that begin as stop-gaps turn out to have many 
purposes beyond that initial stopped gap, and would have been invented 
anyway, if somewhat later, for those other reasons.

LISP may be an example. NAT certainly is.

i mention this because not all ideas which were terrible $originally 
remain terrible in $internet_history.

P Vixie