blkparse(1) — Linux manual page


BLKPARSE(1)                                                      BLKPARSE(1)

NAME         top

       blkparse - produce formatted output of event streams of block devices

SYNOPSIS         top

       blkparse [ options ]

DESCRIPTION         top

       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

OPTIONS         top

       -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

              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

       -S event
              Displays each program's data sorted by program name or io
              event, like Queued, Read, Write and Complete. When -S is
              specified the -s will be ignored.  The capital letters Q,R,W,C
              stand for KB, then q/r/w/c stand for IO.

              If you want to soct programs by how many data they queued, you
              can use:

              blkparse -i sda.blktrace. -q -S Q -o sda.parse

              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
              start:end-time -- Display traces from time start through
              end-time (in ns).

              More verbose marginal on marginal errors

              Display version

TRACE ACTIONS         top

       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.

       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.

       R -- requeue Put a request back on queue.


       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

       g   Cgroup identifier of the cgroup that generated the IO. Note that
           this requires appropriate kernel support (kernel version at least

       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

       z   The absolute time, as local time in your time zone, with no date

       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

       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 operations).

DEFAULT OUTPUT         top

       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

       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.

EXAMPLES         top

       To trace the i/o on the device /dev/sda 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.

AUTHORS         top

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

REPORTING BUGS         top

       Report bugs to <>

COPYRIGHT         top

       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.

SEE ALSO         top

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

COLOPHON         top

       This page is part of the blktrace (Linux block layer I/O tracer)
       project.  Information about the project can be found at [unknown --
       if you know, please contact] It is not known how
       to report bugs for this man page; if you know, please send a mail to  This page was obtained from the project's
       upstream Git repository
       ⟨⟩ on
       2020-11-01.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-05-20.)  If you discover any
       rendering problems in this HTML version of the page, or you believe
       there is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

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

Pages that refer to this page: blkrawverify(1)bno_plot(1)btt(1)iowatcher(1)verify_blkparse(1)blkiomon(8)blktrace(8)btrace(8)btrecord(8)btreplay(8)