NAME | SYNOPSIS | DESCRIPTION | OPTIONS | AUTHORS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON

BTRECORD(8)                                                      BTRECORD(8)

NAME         top

       btrecord - recreate IO loads recorded by blktrace

SYNOPSIS         top

       Usage:

       btrecord [ options ] <dev...>

DESCRIPTION         top

       The btrecord and btreplay tools provide the ability to record and
       replay IOs captured by the blktrace utility. Attempts are made to
       maintain ordering, CPU mappings and time-separation of IOs.

       The blktrace utility provides the ability to collect detailed traces
       from the kernel for each IO processed by the block IO layer. The
       traces provide a complete timeline for each IO processed, including
       detailed information concerning when an IO was first received by the
       block IO layer — indicating the device, CPU number, time stamp, IO
       direction, sector number and IO size (number of sectors). Using this
       information, one is able to replay the IO again on the same machine
       or another set up entirely.

       The basic operating work-flow to replay IOs would be something like:

       -
           Run blktrace to collect traces. Here you specify the
           device or devices that you wish to trace and later replay IOs
         upon. Note:
           the only traces you are interested in are QUEUE requests —
           thus, to save system resources (including storage for traces),
         one could
           specify the -a queue command line option to blktrace.

       -
           While blktrace is running, you run the workload that you
           are interested in.

       -
           When the work load has completed, you stop the blktrace
           utility (thus saving all traces over the complete workload).

       -
           You extract the pertinent IO information from the traces saved by
           blktrace using the btrecord utility. This will parse
           each trace file created by blktrace, and crafty IO descriptions
           to be used in the next phase of the workload processing.

       -
           Once btrecord has successfully created a series of data
           files to be processed, you can run the btreplay utility which
           attempts to generate the same IOs seen during the sample workload
         phase.

OPTIONS         top

       -d <dir>
       --input-directory=<dir>
              Set input directory.  This option requires a single parameter
              providing the directory name for where input files are to be
              found. The default directory is the current directory (.).

       -D <dir>
       --output-directory=<dir>
              Set output directory.  This option requires a single parameter
              providing the directory name for where output files are to be
              found. The default directory is the current directory (.).

       -F
       --find-traces
              Find trace files automatically This option instructs btreplay
              to go find all the trace files in the directory specified
              (either via the -d option, or in the default directory (.).

       -h
       --help
              Show help and exit.

       -V
       --version
              Show version number and exit.

       -m <nanoseconds>
       --max-bunch-time=<nanoseconds>
              The -m option requires a single parameter which specifies an
              amount of time (in nanoseconds) to include in any one bunch of
              IOs that are to be processed. The smaller the value, the
              smaller the number of IOs processed at one time — perhaps
              yielding in more realistic replay.  However, after a certain
              point the amount of overhead per bunch may result in
              additional real replay time, thus yielding less accurate
              replay times.

              The default value is 10,000,000 nanoseconds (10 milliseconds).

       -M <num>
       --max-pkts=<num>
              Set maximum number of packets per bunch.  The -M option
              requires a single parameter which specifies the maximum number
              of IOs to store in a single bunch. As with the -m option,
              smaller values may or may not yield more accurate replay
              times.

              The default value is 8, with a maximum value of up to 512
              being supported.

       -o <basename>
       --output-base=<basename>
              Set base name for output files.  Each output file has 3
              fields:

              1.
                  Device identifier (taken directly from the device name of
                 the
                  blktrace output file).

              2.
                  btrecord base name — by default ``replay''.

              3.
                  The CPU number (again, taken directly from the
                  blktrace output file name).

              This option requires a single parameter that will override the
              default name (replay), and replace it with the specified
              value.

       -v
       --verbose
              Enable verbose output.  This option will output some simple
              statistics at the end of a successful run.  Example output is:

              sdab:0: 580661 pkts (tot), 126030 pkts (replay), 89809 bunches, 1.4 pkts/bunch
              sdab:1: 2559775 pkts (tot), 430172 pkts (replay), 293029 bunches, 1.5 pkts/bunch
              sdab:2: 653559 pkts (tot), 136522 pkts (replay), 102288 bunches, 1.3 pkts/bunch
              sdab:3: 474773 pkts (tot), 117849 pkts (replay), 69572 bunches, 1.7 pkts/bunch

              The meaning of the columns is:

              1.
                   The first field contains the device name and CPU
                 identifier. Thus:
                   sdab:0: means the device sdab and traces on CPU 0.

              2.
                   The second field contains the total number of packets
                 processed for each
                   device file.

              3.
                   The next field shows the number of packets eligible for
                 replay.

              4.
                   The fourth field contains the total number of IO bunches.

              5.
                   The last field shows the average number of IOs per bunch
                 recorded.

AUTHORS         top

       btrecord was written by Alan D. Brunelle.  This man page was created
       from the btreplay documentation by Bas Zoetekouw.

REPORTING BUGS         top

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

COPYRIGHT         top

       Copyright © 2007 Alan D. Brunelle, 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         top

       The full documentation for btreplay can be found in
       /usr/share/doc/blktrace on Debian systems.
       blktrace (8), blkparse (1), btreplay (8)

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 man-pages@man7.org] It is not known how
       to report bugs for this man page; if you know, please send a mail to
       man-pages@man7.org.  This page was obtained from the project's
       upstream Git repository 
       ⟨http://git.kernel.org/cgit/linux/kernel/git/axboe/blktrace.git/⟩ on
       2017-04-25.  If you discover any rendering problems in this HTML ver‐
       sion 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 man‐
       ual page), send a mail to man-pages@man7.org

blktrace git-20071207142532   December  8, 2007                  BTRECORD(8)