e2freefrag is a simple tool to report free space fragmentation on
ext2/3/4 filesystems. It a simple tool which goes through the block
bitmap reporting sizes of free chunks. By default chunksize of 1MB is
used, but a different chunksize can be given using a -c option.

It also reports the min/max/avg size of free chunks and a histogram of
all free chunks.

Here is the output of e2freefrag:
[kalpak@garfield e2fsprogs-1.41.2]# e2freefrag -c 1024 /dev/sda3
Device: /dev/sda3
Blocksize: 4096 bytes

Total blocks: 2560359
Free blocks: 603234 (23.6%)

Total chunks: 10002
Free chunks: 2074 (20.7%)

Min free chunk: 4 KB 
Max free chunk: 98276 KB
Avg. free chunk: 1952 KB

HISTOGRAM OF FREE CHUNK SIZES:
          Range         Free chunks
    4K...    8K- :         326
    8K...   16K- :         186
   16K...   32K- :         124
   32K...   64K- :          88
   64K...  128K- :          83
  128K...  256K- :          74
  256K...  512K- :          58
  512K... 1024K- :          44
    1M...    2M- :          38
    2M...    4M- :          36
    4M...    8M- :         115
    8M...   16M- :          38
   16M...   32M- :          16
   32M...   64M- :           3
   64M...  128M- :           2

Signed-off-by: Kalpak Shah <kalpak.shah@sun.com>
Signed-off-by: Andreas Dilger <adilger@sun.com>