In vmstat output, what does blocked process mean ( b = 1 ) ?

Issue

• In vmstat output analysis - In the "b" column, there is often a blocked process when there is no runnable process (b=1, r=0):

  procs ---------memory---------- ..--io-- --system-- -----cpu------
  r b swpd   free   buff     cache.. bi   bo   in   cs us sy id wa st
  4 0  584 353356 253400 113705408..  2    7    1    1  1  0 99  0  0
  0 0  584 370396 253488 113686320..213 1768 1479 9980  2  1 97  0  0
  1 1  584 372116 253548 113686464..  0  102 1363 5944  1  0 99  0  0
  1 0  584 363424 253592 113694160..  0  902 1419 10058 2  1 97  0  0
  1 1  584 363084 253652 113694248..  0  916 1629 7889  3  0 97  0  0
  0 1  584 354056 253724 113701984.. 18  877 1551 9900  3  1 96  0  0
  0 1  584 352184 253792 113702256.. 26 1126 1494 6634  1  0 98  0  0
  3 0  584 370772 253852 113682080..  0  826 1419 9887  2  1 97  0  0
  0 1  584 371656 253920 113682160..  0 1032 1471 6691  1  0 99  0  0
  1 0  584 363232 253964 113689544..  0  822 1403 8909  1  1 97  0  0
  0 1  584 363684 254012 113689904..  0  954 1384 6119  1  0 99  0  0
  1 0  584 353920 254060 113697632..  0  846 1394 9668  2  2 96  0  0
  0 1  584 354168 254120 113697712..  0  927 1449 5809  1  0 99  0  0
  1 0  584 373448 254168 113677552..  0  829 1493 9389  2  1 97  0  0
  0 1  584 373964 254240 113677632..  0  970 1414 5998  1  0 98  0  0;
  2 0  584 363684 254304 113685360..  6 1651 1439 8446  2  1 96  1  0
  0 1  584 364836 254380 113685424..  0  182 1389 6240  2  1 97  0  0
  1 0  584 354992 254436 113692976..  0 1102 1308 9352  1  1 98  0  0
  0 1  584 355396 254500 113693168..  0  632 1400 4912  1  0 98  0  0
  1 0  584 346056 254564 113700600..  0  862 1426 9563  2  1 97  0  0
  0 1  584 374380 254636 113673032..  0  929 1339 5116  1  0 99  0  0

• If there are no running processes, then what is the blocked process blocked on?