Man Linux: Main Page and Category List


       blkparse - produce formatted output of event streams of block devices


       blkparse [ options ]


       The  blkparse  utility  will  attempt  to combine streams of events for
       various devices on various CPUs, and produce a formatted output of  the
       event  information.   Specifically, it will take the (machine-readable)
       output of the blktrace utility and convert it to a nicely formatted and
       human-readable form.

       As  with  blktrace,  some  details  concerning  blkparse  will  help in
       understanding the command line options presented below.

       - By default, blkparse expects to run in a  post-processing  mode;  one
         where the trace events have been saved by a previous run of blktrace,
         and blkparse is combining event streams and dumping formatted data.

         blkparse may be run in a live manner concurrently  with  blktrace  by
         specifying  -i  -  to blkparse, and combining it with the live option
         for blktrace.  An example would be:

            % blktrace -d /dev/sda -o - | blkparse -i -

       - You can set how many blkparse batches event reads via the -b  option,
         the default is to handle events in batches of 512.

       - If  you  have  saved  event  traces in blktrace with different output
         names (via the -o option to blktrace),  you  must  specify  the  same
         input name via the -i option.

       - The  format  of  the  output  data can be controlled via the -f or -F
         options -- see OUTPUT DESCRIPTION AND FORMATTING for details.

       By default, blkparse sends formatted data to standard output. This  may
       be changed via the -o option, or text output can be disabled via the -O
       option. A merged binary stream can be produced using the -d option.


       -b batch
              Standard input read batching

       -i file
              Specifies  base   name   for   input   files   --   default   is

              As  noted above, specifying -i - runs in live mode with blktrace
              (reading data from standard in).

       -F typ,fmt
       -f fmt
              Sets output format (See OUTPUT DESCRIPTION  AND  FORMATTING  for

              The -f form specifies a format for all events

              The  -F form allows one to specify a format for a specific event
              type. The single-character  typ  field  is  one  of  the  action
              specifiers described in ACTION IDENTIFIERS.

              When  -d is specified, this will stop messages from being output
              to the file. (Can seriously reduce the  size  of  the  resultant
              file when using the CFQ I/O scheduler.)

              Hash processes by name, not by PID

       -o file
              Output file

              Do not produce text output, used for binary (-d) only

       -d file
              Binary output file

              Quiet mode

              Displays data sorted by program

              Display time deltas per IO

       -w span
              Display traces for the span specified -- where span can be:
              end-time -- Display traces from time 0 through end-time (in ns)
              start:end-time   --  Display  traces  from  time  start  through
              end-time (in ns).

              More verbose marginal on marginal errors

              Display version


       The following trace actions are recognised:

       C -- complete A previously issued  request  has  been  completed.   The
           output  will detail the sector and size of that request, as well as
           the success or failure of it.

       D -- issued A request that previously resided on the block layer  queue
           or in the i/o scheduler has been sent to the driver.

       I -- inserted A request is being sent to the i/o scheduler for addition
           to the internal queue and later service by the driver. The  request
           is fully formed at this time.

       Q  --  queued This notes intent to queue i/o at the given location.  No
           real requests exists yet.

       B -- bounced The data pages attached to this bio are not  reachable  by
           the  hardware  and must be bounced to a lower memory location. This
           causes a big slowdown in i/o performance, since the  data  must  be
           copied to/from kernel buffers. Usually this can be fixed with using
           better hardware -- either a better i/o controller,  or  a  platform
           with an IOMMU.

       M  --  back merge A previously inserted request exists that ends on the
           boundary of where this i/o begins, so the i/o scheduler  can  merge
           them together.

       F  --  front merge Same as the back merge, except this i/o ends where a
           previously inserted requests starts.

       M --front or back merge One of the above

       M -- front or back merge One of the above.

       G -- get request To send any type of  request  to  a  block  device,  a
           struct request container must be allocated first.

       S  --  sleep  No  available  request  structures were available, so the
           issuer has to wait for one to be freed.

       P -- plug When i/o is queued to a previously empty block device  queue,
           Linux will plug the queue in anticipation of future ios being added
           before this data is needed.

       U -- unplug Some request data  already  queued  in  the  device,  start
           sending  requests to the driver. This may happen automatically if a
           timeout period has passed (see  next  entry)  or  if  a  number  of
           requests have been added to the queue.

       T  --  unplug  due  to timer If nobody requests the i/o that was queued
           after plugging the queue, Linux will automatically unplug it  after
           a defined period has passed.

       X  --  split  On  raid  or  device  mapper  setups, an incoming i/o may
           straddle a device or internal zone and needs to be chopped up  into
           smaller pieces for service. This may indicate a performance problem
           due to a bad setup of that raid/dm device, but  may  also  just  be
           part  of  normal boundary conditions. dm is notably bad at this and
           will clone lots of i/o.

       A -- remap For stacked devices, incoming  i/o  is  remapped  to  device
           below it in the i/o stack. The remap action details what exactly is
           being remapped to what.


       The output from blkparse  can  be  tailored  for  specific  use  --  in
       particular,  to  ease  parsing of output, and/or limit output fields to
       those the user wants to see. The data for fields which  can  be  output

       a   Action, a (small) string (1 or 2 characters) -- see table below for
           more details

       c   CPU id

       C   Command

       d   RWBS field, a (small) string (1-3 characters)  -- see section below
           for more details

       D   7-character  string  containing  the major and minor numbers of the
           event’s device (separated by a comma).

       e   Error value

       m   Minor number of event’s device.

       M   Major number of event’s device.

       n   Number of blocks

       N   Number of bytes

       p   Process ID

       P   Display packet data -- series of hexadecimal values

       s   Sequence numbers

       S   Sector number

       t   Time stamp (nanoseconds)

       T   Time stamp (seconds)

       u   Elapsed value in microseconds (-t command line option)

       U   Payload unsigned integer

       Note that the user can optionally  specify  field  display  width,  and
       optionally  a  left-aligned  specifier. These precede field specifiers,
       with a ’%’ character, followed by the optional left-alignment specifier
       (-) followed by the width (a decimal number) and then the field.

       Thus,  to  specify  the  command  in  a 12-character field that is left

           -f "%-12C"


       The following table shows the various actions which may be output:

       A      IO was remapped to a different device

       B      IO bounced

       C      IO completion

       D      IO issued to driver

       F      IO front merged with request on queue

       G      Get request

       I      IO inserted onto request queue

       M      IO back merged with request on queue

       P      Plug request

       Q      IO handled by request queue code

       S      Sleep request

       T      Unplug due to timeout

       U      Unplug request

       X      Split


       This is a small string containing at least one character (’R’ for read,
       ’W’  for  write,  or  ’D’  for block discard operation), and optionally
       either  a  ’B’  (for  barrier  operations)  or  ’S’  (for   synchronous


       The standard header (or initial fields displayed) include:

           "%D %2c %8s %5T.%9t %5p %2a %3d"

       Breaking this down:

       %D     Displays the event’s device major/minor as: %3d,%-3d.

       %2c    CPU ID (2-character field).

       %8s    Sequence number

              5-character  field for the seconds portion of the time stamp and
              a 9-character field for the nanoseconds in the time stamp.

       %5p    5-character field for the process ID.

       %2a    2-character field for one of the actions.

       %3d    3-character field for the RWBS data.

              Seeing this in action:

                  8,0    3        1     0.000000000   697  G   W  223490  +  8

              The  header  is the data in this line up to the 223490 (starting
              block).  The default output for all event  types  includes  this


       C -- complete
           If  a  payload  is  present,  this is presented between parenthesis
           following the header, followed by the error value.

           If no payload is present, the  sector  and  number  of  blocks  are
           presented  (with  an  intervening  plus  (+)  character). If the -t
           option was specified, then the elapsed time is presented. In either
           case, it is followed by the error value for the completion.

       B -- bounced
       D -- issued
       I -- inserted
       Q -- queued
           If  a  payload  is  present, the number of payload bytes is output,
           followed by the payload in hexadecimal between parenthesis.

           If no payload is present, the  sector  and  number  of  blocks  are
           presented  (with  an  intervening  plus  (+)  character). If the -t
           option was specified,  then  the  elapsed  time  is  presented  (in
           parenthesis).  In  either  case,  it  is  followed  by  the command
           associated with the event (surrounded by square brackets).

       F -- front merge
       G -- get request
       M -- back merge
       S -- sleep
           The starting sector  and  number  of  blocks  is  output  (with  an
           intervening plus (+) character), followed by the command associated
           with the event (surrounded by square brackets).

       P -- plug
           The  command  associated  with  the  event  (surrounded  by  square
           brackets) is output.

       U -- unplug
       T -- unplug due to timer
           The  command  associated  with  the  event  (surrounded  by  square
           brackets)  is  output,  followed  by   the   number   of   requests

       X -- split
           The  original starting sector followed by the new sector (separated
           by a slash (/) is output, followed by the command  associated  with
           the event (surrounded by square brackets).

       A -- remap
           Sector  and  length  is  output, along with the original device and
           sector offset.


       To trace the i/o on the device /dev/hda and parse the output  to  human
       readable form, use the following command:

           % blktrace -d /dev/sda -o - | blkparse -i -

       (see  blktrace  (8)  for more information).  This same behaviour can be
       achieve with the convenience script btrace.  The command

           % btrace /dev/sda

       has exactly the same effect as the previous command. See btrace (8) for
       more information.

       To  trace  the i/o on a device and save the output for later processing
       with blkparse, use blktrace like this:

           % blktrace /dev/sda /dev/sdb

       This will trace i/o on the devices /dev/sda and /dev/sdb and  save  the
       recorded information in the files sda and sdb in the current directory,
       for the two different devices, respectively.   This  trace  information
       can later be parsed by the blkparse utility:

           % blkparse sda sdb

       which  will output the previously recorded tracing information in human
       readable form to stdout.


       blkparse was written by Jens Axboe, Alan D. Brunelle and Nathan  Scott.
       This  man  page  was  created  from  the  blktrace documentation by Bas


       Report bugs to <>


       Copyright © 2006 Jens Axboe, Alan D. Brunelle and Nathan Scott.
       This is free software.  You may redistribute copies  of  it  under  the
       terms       of       the      GNU      General      Public      License
       <>.  There is NO WARRANTY,  to  the
       extent permitted by law.
       This  manual  page  was  created  for  Debian by Bas Zoetekouw.  It was
       derived from the documentation provided by the authors and  it  may  be
       used,  distributed  and  modified  under  the  terms of the GNU General
       Public License, version 2.
       On Debian systems, the text of the GNU General Public  License  can  be
       found in /usr/share/common-licenses/GPL-2.


       btrace  (8),  blktrace  (8), verify_blkparse (1), blkrawverify (1), btt