Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!killer!ames!oliveb!amiga!jimm
From: jimm@amiga.UUCP (Jim Mackraz)
Newsgroups: comp.sys.amiga.tech
Subject: Re: free memory defragmentation
Message-ID: <3009@amiga.UUCP>
Date: 11 Oct 88 23:14:52 GMT
References: <9887@cup.portal.com>
Reply-To: jimm@cloyd.UUCP (Jim Mackraz)
Organization: Commodore-Amiga Inc, Los Gatos CA
Lines: 50

In article <9887@cup.portal.com> dan-hankins@cup.portal.com writes:
)I am considering writing a utility to take the free memory heap and
)defragment it.  This would involve looking at each of the nodes, reading
)them out into a linked list, sorting the linked list, and then
)concatenating all the adjacent blocks and then rebuilding the heap.

The list is sorted, and adjacent blocks are concatenated, all of the
time.

)This seems like such a simple idea, it amazes me that it has not occurred
)to anyone before.  Has it?  Would I be re-inventing the wheel? 

I think Carl thought of it, too.

)If so, where could I find this utility?  I have a need for it.

It is called FreeMem(), a function of the Exec in ROM.	;^)

)If no one has written one before, is there some quirk of the opsys that
)would prevent me from doing it?

You could call it a quirk, I guess.

)I already envision that the second version would intercept calls to
)the system allocation and de-allocation functions and run in the background,
)only doing the de-fragmentation when a block is returned to the heap or
)when an allocation request fails.

FreeMem().

)Dan Hankins

	jimm

By the way: memory fragmentation on the Amiga occurs because there are
actually allocated sections of memory between the freed chunks.  There's
been a lot of discussion on this already.

Note that you can't concatenate two non-adjacent chunks.

If you think you have identified a condition where there are adjacent
free chunks in the free list (or an unsorted free list), please reproduce
and mail in a floppy.  I don't think so, though.


-- 
	Jim Mackraz, I and I Computing	  
	amiga!jimm	BIX:jmackraz
Opinions are my own.  Comments regarding the Amiga operating system, and
all others, are not to be taken as Commodore official policy.