[gclist] Fragmentation terminology

[Nick Barnes]

>  || Fragmentation is when an allocator cannot satisfy a request [without
>  || going to the OS for more memory] despite there being sufficient unused
>  || space.
> 
> Picking nits (since you are discussing terminology): in OS circles,
> we call fragmentation the fact that there are unused/unusable holes
> in the memory allocation.  So there are degrees of fragmentation;
> e.g. it makes sense to say "a bit of fragmentation doesn't hurt",
> "this disk is severely fragmented".  Under your definition these
> sentences would not make sense.

Yes, of course, my definition above is sloppy. Of course a finished
definition must allow for these uses. There are problems with using a
single number to describe fragmentation (which is fundamentally a
multi-dimensional effect) and therefore with saying "a lot of
fragmentation", but one can get away with it in most circumstances.

Nick B