Provided by: blktrace_1.1.0-2_i386 bug

NAME

       blktrace - generate traces of the i/o traffic on block devices

SYNOPSIS

       blktrace  -d  dev [ -r debugfs_path ] [ -o output ] [-k ] [ -w time ] [
       -a action ] [ -A action_mask ] [ -v ]

DESCRIPTION

       blktrace is a block layer IO tracing mechanism which provides  detailed
       information  about request queue operations up to user space. There are
       three major components: a kernel component, a utility to record the i/o
       trace  information  for  the  kernel  to  user  space, and utilities to
       analyse and view  the  trace  information.   This  man  page  describes
       blktrace,  which records the i/o event trace information for a specific
       block device to a file.

       The blktrace utility extracts event traces from  the  kernel  (via  the
       relaying  through  the  debug  file  system).  Some  background details
       concerning the run-time behaviour of blktrace will help  to  understand
       some of the more arcane command line options:

       - blktrace  receives  data from the kernel in buffers passed up through
         the debug file system (relay). Each device being traced  has  a  file
         created  in  the mounted directory for the debugfs, which defaults to
         /sys/kernel/debug -- this can be overridden with the -r command  line
         argument.

       - blktrace  defaults  to  collecting  all events that can be traced. To
         limit the events being captured, you can specify one or  more  filter
         masks via the -a option.

         Alternatively,   one   may   specify  the  entire  mask  utilising  a
         hexadecimal value that is version-specific.  (Requires  understanding
         of the internal representation of the filter mask.)

       - As  noted  above,  the  events  are passed up via a series of buffers
         stored into debugfs files. The size and  number  of  buffers  can  be
         specified via the -b and -n arguments respectively.

       - blktrace  stores  the  extracted  data into files stored in the local
         directory.  The  format  of  the   file   names   is   (by   default)
         device.blktrace.cpu, where device is the base device name (e.g, if we
         are tracing /dev/sda, the base device name would  be  sda);  and  cpu
         identifies a CPU for the event stream.

         The  device  portion of the event file name can be changed via the -o
         option.

       - blktrace may also be run concurrently with blkparse to  produce  live
         output -- to do this specify -o - for blktrace.

       - The default behaviour for blktrace is to run forever until explicitly
         killed by the user (via a control-C, or sending SIGINT signal to  the
         process  via invocation the kill (1) utility). Also you can specify a
         run-time duration for blktrace via the -w  option  --  then  blktrace
         will run for the specified number of seconds, and then halt.

OPTIONS

       -A hex-mask
       --set-mask=hex-mask
              Set filter mask to hex-mask (see below for masks)

       -a mask
       --act-mask=mask
              Add mask to current filter (see below for masks)

       -b size
       --buffer-size=size
              Specifies buffer size for event extraction (scaled by 1024). The
              default buffer size is 512KiB.

       -d dev
       --dev=dev
              Adds dev as a device to trace

       -I file
       --input-devs=file
              Adds the devices found in file as devices to trace

       -n num-sub
       --num-sub-buffers=num-sub
              Specifies number of buffers to use. blktrace defaults to  4  sub
              buffers.

       -l
       --listen
              Run in network listen mode (blktrace server)

       -h hostname
       --host=hostname
              Run in network client mode, connecting to the given host

       -p number
       --port=number
              Network port to use (default 8462)

       -s
       --no-sendfile
              Make the network client NOT use sendfile() to transfer data

       -o basename
       --output=basename
              Specifies    base    name    for   input   files.   Default   is
              device.blktrace.cpu.  Specifying -o - runs  in  live  mode  with
              blkparse (writing data to standard out).

       -D dir
       --output-dir=dir
              Prepend file to output file name(s)

              This  only  works when supplying a single device, or when piping
              the output via "-o -" with multiple devices.

       -r rel-path
       --relay=rel-path
              Specifies debugfs mount point

       -v
       --version
              Outputs version

       -V
       --version
              Outputs version

       -w seconds
       --stopwatch=seconds
              Sets run time to the number of seconds specified

FILTER MASKS

       The following masks may be passed with  the  -a  command  line  option,
       multiple filters may be combined via multiple -a command line options.

              barrier: barrier attribute
              complete: completed by driver
              fs: requests
              issue: issued to driver
              pc: packet command events
              queue: queue operations
              read: read traces
              requeue: requeue operations
              sync: synchronous attribute
              write: write traces
              notify: trace messages
              drv_data: additional driver specific trace

REQUEST TYPES

       blktrace  distinguishes between two types of block layer requests, file
       system and SCSI commands. The former are dubbed fs requests, the latter
       pc  requests.  File  system  requests are normal read/write operations,
       i.e.  any type of read or write from a  specific  disk  location  at  a
       given size. These requests typically originate from a user process, but
       they may also be initiated by the vm flushing dirty data to disk or the
       file  system  syncing a super or journal block to disk. pc requests are
       SCSI commands. blktrace sends the command data block as  a  payload  so
       that blkparse can decode it.

EXAMPLES

       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 -

       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.  See blkparse (1) for more information.

AUTHORS

       blktrace  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

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

COPYRIGHT

       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
       <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  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

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