Listing 2. A smaller trim threshold might save space.

branzo@betelgeuse:~/malloc_debug$ ./Listing_1 128

Allocating 100k, trim threshhold is set to 131072
Arena 0:
system bytes     =     103724
in use bytes     =     100012
Total (incl. mmap):
system bytes     =     103724
in use bytes     =     100012
max mmap regions =          0
max mmap bytes   =          0

Now freeing 100k
Arena 0:
system bytes     =     103724
in use bytes     =          4
Total (incl. mmap):
system bytes     =     103724
in use bytes     =          4
max mmap regions =          0
max mmap bytes   =          0

branzo@betelgeuse:~/malloc_debug$ ./Listing_1 64

Allocating 100k, trim threshhold is set to 65536
Arena 0:
system bytes     =     103724
in use bytes     =     100012
Total (incl. mmap):
system bytes     =     103724
in use bytes     =     100012
max mmap regions =          0
max mmap bytes   =          0

Now freeing 100k
Arena 0:
system bytes     =       1324
in use bytes     =          4
Total (incl. mmap):
system bytes     =       1324
in use bytes     =          4
max mmap regions =          0
max mmap bytes   =          0