mcdonald@fornax.UUCP (Ken Mcdonald) (02/06/89)
Does anyone out there know the practical limits of the memory manager?
As in:
I want to write an application that will make heavy use of relocateable
blocks--as in, HEAVY. In degenerate cases, I could be running about
10,000 relocateable blocks/250k of heap space. (The limit, of course,
is about 20,000/250k, at which point the entire heap is taken up with
memory manager info, leaving no room for your own data!) Question: when
will the memory manager start to complain. Complaining consists of slowness,
crashes, or other undesireable behaviour.
Some notes to aid you in your advice...I will be arranging things so that
all nonrelocateable blocks are at the bottom of the heap, and all
relocateable blocks are unlocked when a request for more memory is
issued. This means that the memory manager can get every last by out
of the heap. I will be doing lots of things like increasing or decreasing
the sizes of blocks, and, in general, proby working the memory manager's
little fingers to the bone.
So, comments?
Finally, is there Pascal source available (preferably free) to set up a
pseudo-heap (by grabbing a big array, for instance), and then doing
transparent dynamic allocation in the pseudo-heap? By transparent, I
mean that it keeps track of what is valid and what's not, and throws
something away when it should be thrown away--like LISP garbage collection,
except I want variable-size elements in the pseudo-heap. The memory
manager isn't really suitable for something like this.
Thanks for all the help,
Ken McDonald
{...!ubc-cs!mcdonald@fornax.uucp}SIAC@applelink.apple.com (Eric Ulevik) (02/07/89)
In article <868@fornax.UUCP> mcdonald@fornax.UUCP (Ken Mcdonald) writes: > I want to write an application that will make heavy use of relocateable > blocks--as in, HEAVY. In degenerate cases, I could be running about > 10,000 relocateable blocks/250k of heap space. Well, I once tried to store lots of data in relocatable blocks. On a Mac Plus, with over 1,000 or so relocatable blocks, the program slowed down by about 3 times, due to all the block shuffling that the memory manager was doing. You don't want to do this. The memory manager won't handle that much data. I recommend you perform your own memory management on a large fixed block of memory. You may or may not want to allow relocatable blocks. Also, some useful references to quick methods of dealing with lots of little pieces of data can be found in the Smalltalk world. There are some good algorithms for dealing with this kind of problem - I recall what Actor (a Smalltalk-like language running under Microsoft Windows) does. Eric Ulevik email: SIAC@applelink.apple.com