What is the role of /proc/fs/jbd2/sda6-8/info in Ubuntu?

Question

I am using the Ubuntu 14.04. Today I was going through the file system and I found that in the file at

/proc/fs/jbd2/sda6-8/info

following thing mentioned.

  9286 transactions (8421 requested), each up to 8192 blocks

average:

  0ms waiting for transaction
  0ms request delay
  1612ms running transaction
  0ms transaction was being locked
  0ms flushing data (in ordered mode)
  36ms logging transaction
  82093us average transaction commit time
  90 handles per transaction
  8 blocks per transaction
  9 logged blocks per transaction

What is meant by all the above?

What is the role of the file /proc/fs/jbd2/sda6-8/info in Ubuntu? What is the significance of all the above?

Answer 1

According to wiki.kernel.org FAQ

/proc/fs/jbd2/partition/info file shows the average statistics from the /proc/fs/jbd2/partition/history file since the file system was first mounted.

Executing cat /proc/fs/jbd2/partition/info gives:

56 transaction, each upto 2048 blocks
average: 
 0ms waiting for transaction
 57671ms running transaction
 0ms transaction was being locked
 28ms flushing data (in ordered mode)
 14ms logging transaction
 2383 handles per transaction
 6 blocks per transaction
 7 logged blocks per transaction

Also the purpose of /proc/fs/jbd2/partition/history file is to provide information on the behaviour of the ext4 journaling layer (JBD2).

cat /proc/fs/jbd2/partition/history gives:

R/C  tid   wait  run   lock  flush log   hndls  block inlog ctime write drop  close
R    7102  0     5000  0     1424  4     68681  5     6    
R    7103  0     5000  0     1644  4     64579  9     10   
R    7104  0     5000  0     856   32    38719  11    12   
R    7105  0     5000  0     1052  0     47142  12    13   
R    7106  0     5000  0     1172  16    56028  11    12   
R    7107  0     5000  0     1416  4     71047  11    12   
R    7108  0     5000  0     1640  4     81125  5     6    
R    7109  0     5000  0     1616  4     77314  6     7    
R    7110  0     5000  0     1640  0     76111  5     6    
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