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From: "drepper at redhat dot com" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug libc/2531] missing call or documentation for malloc_trim() ...
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------- Additional Comments From drepper at redhat dot com  2006-04-26 02:15 -------
Why don't you make your little program write out the data:

#include <unistd.h>
#include <stdlib.h>
#include <malloc.h>
#include <stdio.h>
int
main (int argc, char *argv[])
{
  char cmd[100];
  snprintf (cmd, sizeof (cmd), "grep heap /proc/%d/maps || echo no heap",
            getpid ());
  void *before = sbrk (0);
  system (cmd);
  int max = 10000000;
  char **p1 = (char **) malloc (max * sizeof (char *));
  for (int x = 0; x < max; x++)
    {
      p1[x] = (char *) malloc (29);
    }
  for (int x = 0; x < max; x++)
    {
      free (p1[x]);
    }
  free (p1);
  void *middle = sbrk (0);
  system (cmd);
  malloc_trim (0);
  void *after = sbrk (0);
  system (cmd);
  printf ("before = %p, middle = %p, after = %p\n", before, middle, after);
  return 0;
}


When I run this I see

no heap
00501000-1cee1000 rw-p 00501000 00:00 0                                  [heap]
00501000-00502000 rw-p 00501000 00:00 0                                  [heap]
before = 0x501000, middle = 0x1cee1000, after = 0x502000


This clearly shows that

a) libc returns all memory if malloc_trim is used
b) the kernel frees all memory.


So, what's the problem?

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID


http://sourceware.org/bugzilla/show_bug.cgi?id=2531

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