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CentOS 7.0 - man page for blkparse (centos section 1)

BLKPARSE(1)									      BLKPARSE(1)

       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 var-
       ious 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 for-
       matted 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

       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.

       -A hex-mask
	      Set filter mask to hex-mask, see blktrace (8) for masks

       -a mask
	      Add mask to current filter, see blktrace (8) for masks

       -D dir
	      Prepend dir to input file names

       -b batch
	      Standard input read batching

       -i file
	      Specifies base name for input files -- default is device.blktrace.cpu.

	      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 details.)

	      The -f form specifies a format for all events

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

	      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

       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  perfor-
	   mance, 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

       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  pars-
       ing  of	output,  and/or  limit output fields to those the user wants to see. The data for
       fields which can be output include:

       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 (sepa-
	   rated 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 aligned:

	   -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 operations).

       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 [kjournald]

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

       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 pay-
	   load 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  associ-
	   ated 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 (+) char-
	   acter), followed by the command associated with the event (surrounded by square brack-

       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, fol-
	   lowed by the number of requests outstanding.

       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 brack-

       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 con-
       venience 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,  respec-
       tively.	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

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

       Report bugs to <linux-btrace@vger.kernel.org>

       Copyright (C) 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 Gen-
       eral Public License <http://www.gnu.org/licenses/gpl.html>.  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 docu-
       mentation 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

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

blktrace git-20070306202522		  March  6, 2007			      BLKPARSE(1)

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