# xfs_db -r -c "freesp -s" /dev/root 
   from      to extents  blocks    pct
      1       1   10863   10863   0.01
      2       3    7103   16915   0.02
      4       7    4986   26448   0.04
      8      15   14642  188888   0.25
     16      31    1028   22301   0.03
     32      63     564   25682   0.03
     64     127     572   51867   0.07
    128     255     368   63850   0.09
    256     511     263   95729   0.13
    512    1023     216  159546   0.22
   1024    2047     193  277090   0.37
   2048    4095     164  467557   0.63
   4096    8191     158  951352   1.28
   8192   16383     134 1560572   2.11
  16384   32767      94 2139129   2.89
  32768   65535      59 2722139   3.67
  65536  131071      42 3780134   5.10
 131072  262143      28 5049829   6.82
 262144  524287       8 2779412   3.75
 524288 1048575       7 4982808   6.73
1048576 2097151       3 5586440   7.54
2097152 4194303       2 4626238   6.24
4194304 8388607       5 30000677  40.50
8388608 16777215       1 8499381  11.47
total free extents 41503
total free blocks 74084847
average free extent size 1785.05