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From: tasayco@phoenix.Princeton.EDU (Maria Tasayco)
Newsgroups: comp.os.minix
Subject: free memory
Keywords: minix, free memory
Message-ID: <3189@idunno.Princeton.EDU>
Date: 8 Oct 90 00:37:24 GMT
Sender: news@idunno.Princeton.EDU
Organization: Princeton University, Princeton, New Jersey
Lines: 35

I wrote a simple program to find out how much free memory is there in
the heap (or the largest available chunk), at least I hoped that would
be the result! Instead I found that it returns a much smaller value
(my setup is an Atari 1040ST with 1MB and around 430kB of free memory
when Minix boots up): it returns consistently 56kB. I looked into the
source for sbrk() and it looked OK. Maybe this behaviour is to be
expected but I don't see why. 

The program is short and follows:

#include <stdio.h>

#define ulong unsigned long

extern char *sbrk();

int main()
{
  char *tp, *tp0, *tp1;
  long top = 0;

  /* Get memory top (at least that's what I think it should do) */
  tp0 = sbrk((int)0);
  /* Try to get 1kB until no more available */
  while ((tp = sbrk((int)1024)) != (char *)-1) tp1 = tp;
  /* Show the result */
  printf("free memory = %ldkb\n", ((ulong)tp1 - (ulong)tp0)/1024);

  return(0);
}

Any comments are welcome (even if they tell me how dump I am).

	Francisco Figueirido
	e-mail: tasayco@phoenix.princeton.edu