Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!usc!rutgers!cbmvax!jjszucs
From: jjszucs@cbmvax.commodore.com (John J. Szucs)
Newsgroups: comp.sys.amiga
Subject: Re: A few questions...
Message-ID: <13250@cbmvax.commodore.com>
Date: 17 Jul 90 15:10:55 GMT
References: <51083@iuvax.cs.indiana.edu>
Reply-To: jjszucs@cbmvax (John J. Szucs)
Organization: Commodore, West Chester, PA
Lines: 81

In article <51083@iuvax.cs.indiana.edu> amhartma@silver.ucs.indiana.edu (Andy Hartman - AmigaMan) writes:
>I have a few questions:
>	1) Is there a program which will un-fragment memory?
>

Defragmentation of memory by moving allocated blocks in memory (the memory
equivalent of disk defragmentation) is not possible under the current
Amiga memory management design because applications receive a direct pointer to
the memory that they allocate. If that memory is moved, there is no way for
the program to know that the pointer they received from Exec when they
made the allocation is now invalid.

However, Exec will automatically coalesce memory chunks as memory is freed
by programs in the system. For example, if a block of memory is allocated
as follows:

+-----------+---------------------------+-----------+
| 1/2K Free | 1K Allocated by Program A | 1/2K Free |
|-----------+---------------------------+-----------+

and program A frees the memory it allocated, the above will be coalesce into
one 2K block of free memory.

>	2) Why (on my 3 meg machine) do I get the following when I type 
>	   "avail"
>
>		In-use    Largest
>		------    -------
>		129648    2041520
>
>Where is the 3rd meg? (I interrupt WB immediately upon boot so nothing loads..)
>(Note:  I left out 2 fields of the actual output.)

The full output from avail is probably similar to this (this is from my 5 meg
A2500 with 1 meg of chip RAM running Kickstart/Workbench Release 2.0):

Type	Available  In-Use  Maximum  Largest
chip	   715320  332232  1047552   714976
fast	  3509536  684768  4194304  3506216
total	  4224856 1017000  5241856  3506216

The Available column indicates the currently available number of bytes of
chip RAM, fast RAM, and all RAM in the system.

The In-Use column indicates the number of bytes of chip RAM, fast RAM,
and all RAM currently allocated in the system.

The Maximum column indicates the total number of bytes of chip RAM, fast
RAM, and all RAM in the system (available or in-use). On a 3MB system,
assuming 1MB of chip RAM, and 2MB of fast RAM, the Maximum column should read:

Type	...	Maximum
chip		1047552
fast		2097152
total		3145908

Note that these figures may not exactly match the results on your system,
but they should be fairly close.

The Largest column indicates the size of the largest contiguous block of
memory of chip RAM, fast RAM, or any RAM. For example, if on a 1MB system,
the memory is allocated as follows:

|--------------------------------1024K-------------------------------|

+-----------+--------+--------------+--------+-------------+---------+
|400K system|32K free|135K Program A|96K free|90K Program B|271K free|
+-----------+--------+--------------+--------+-------------+---------+

The Largest column would should 271K.

>* Andy Hartman       | I'd deny half of this crap anyway!| "Somedays, you just

================================================================================
|| John J. Szucs                    || The opinions expressed are my own and  ||
|| Systems Evaluation Group         || in no way represent the opinions or    ||
|| Product Assurance Department     || policies of Commodore Technology, Inc. ||
|| Commodore Technology, Inc.       || or any associated entity.              ||
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