🚀 go-pugleaf

In article <10926@s.ms.uky.edu> sean@ms.uky.edu (Sean Casey) writes:

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>Why? Seems to me that resource allocation is an infrequently done thing.

Resource allocation is infrequently done in a language like FORTRAN
which has a static view of the world and doesn't allow users to
allocate and deallocate memory.  In something more modern, like Modula
2, Pascal, Lisp, or C, this is no longer true.  Consider linked lists,
trees, etc.; to manage these sorts of structures in an application
program you're continuously grabbing new memory and (hopefully)
returning it to the system when you're done with it.  Even if you're
just running FORTRAN or BASIC, the translator is going to allocate
memory dynamically.

>It also seems to me that resources could be tracked with bitmaps. Where
>is the serious speed/memory degradation?

OK.  Let's keep track of every byte of RAM in the Amiga.  If we allow
for 8MB of RAM, then we need an 8Mb map, which comes to a megabyte.
The alternatives are to increase the granularity of our map or keep it
on disk.  It won't fit on a floppy, and even on a hard drive
performance would be hampered.  If we increase the granularity to,
say, a "paragraph" (Intel's term for 16 bytes if memory serves), then
8MB is thought of as 512k paragraphs, so the bitmap can fit in 64kB.
This is still a considerable amount of memory, and results in wasted
space if the user doesn't use memory in 16 byte chunks.

Of course, it's not necessary to worry about memory that's not
actually present.  Assuming memory's allocated on a word basis,
though,  a sixteenth of your memory's gonna be just bitmaps, and this
is pretty significant.

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-- Jeff (martens@cis.ohio-state.edu)