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   btrecord    ( 8 )

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Имя (Name)

btrecord - recreate IO loads recorded by blktrace

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Синопсис (Synopsis)

Usage:

       btrecord [ options ] <dev...>

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Описание (Description)

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.

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Параметры (Options)

-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.

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