Currently both ext4 and ldiskfs provide /proc/fs/

/<dev>/mb_groups output. This file is referenced in many kernel documents however other than noting that it's providing data on buddy group cache info, it doesn't bother documenting any further.

Below is sample output from this file, it would be extremely useful for this to be fully documented and understood.

#0 : 23147 1 9280 [ 1 1 0 1 0 1 1 0 0 1 0 1 1 2 ]
#1 : 1156 41 1025 [ 42 15 5 3 3 3 2 2 2 0 0 0 0 0 ]
#2 : 782 46 8194 [ 38 28 10 5 4 3 1 1 1 0 0 0 0 0 ]
#3 : 624 7 1025 [ 10 9 5 4 2 2 1 1 1 0 0 0 0 0 ]
#4 : 1065 6 12802 [ 3 5 3 2 2 1 1 1 1 1 0 0 0 0 ]
#5 : 1023 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 0 0 0 ]
#6 : 0 0 32768 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ]
#7 : 1023 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 0 0 0 ]
#8 : 1022 1 19458 [ 0 1 1 1 1 1 1 1 1 1 0 0 0 0 ]
#9 : 1784 4 1025 [ 2 3 2 3 3 3 1 2 1 2 0 0 0 0 ]