dt-usersguide.txt

Linux磁盘测试的源代码,测试磁盘的读写性能

              Syntax:
                  passes=value     The number of passes to perform.


          4.30  Data Pattern "pattern=" Option.

               This option specifies a 32 bit hexadecimal data  pattern  to
          be used for the data pattern.  dt has 12 built-in patterns, which
          it alternates through when running multiple passes.  The  default
          data patterns are:

              0x39c39c39, 0x00ff00ff, 0x0f0f0f0f, 0xc6dec6de, 0x6db6db6d, 0x00000000,
              0xffffffff, 0xaaaaaaaa, 0x33333333, 0x26673333, 0x66673326, 0x71c7c71c

          You can also specify the special keyword "incr" to use an  incre-
          menting  data  pattern,  or  specify a character string (normally
          contained within single or double quotes).

              Syntax:
                  pattern=value    The 32 bit hex data pattern to use.
              or  pattern=iot      Use DJ's IOT test pattern.
              or  pattern=incr     Use an incrementing data pattern.
              or  pattern=string   The string to use for the data pattern.

          So, what is DJ's IOT test pattern?  This pattern places the logi-
          cal  block  address  (lba)  in  the  first word (4 bytes) of each
          block, with (lba+=0x01010101) being placed in all remaining words
          in the data block (512 bytes by default).  In this way, the logi-
          cal block is seeded throughout each word in the block.

               When specifying a pattern string via  "pattern=string",  the
          following special mapping occors:

              Pattern String Mapping:
                 \\ = Backslash   \a = Alert (bell)   \b = Backspace
                 \f = Formfeed    \n = Newline        \r = Carriage Return
                 \t = Tab         \v = Vertical Tab   \e or \E = Escape
                 \ddd = Octal Value    \xdd or \Xdd = Hexadecimal Value






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          4.31  File Position "position=" Option.

               This option specifies a byte offset  to  seek  to  prior  to
          starting each pass of each test.

              Syntax:
                  position=offset  Position to offset before testing.


          4.32  Multiple Processes "procs=" Option.

               This option specifies the number of  processes  to  initiate
          performing  the same test.  This option allows an easy method for
          initiating multiple I/O requests to a single device or file  sys-
          tem.

          Special Notes:
            o  The per process limit on  Tru64  UNIX  is  64,  and  can  be
               queried by using the "sysconfig_-q_proc" command.
            o  Spawning many processes can render your system useless, well
               at least very slow, and consumes large amounts of swap space
               (make sure you have plenty!).
            o  The parent process simply monitors  (waits  for)  all  child
               prcoesses.
            o  When writing to a file  system,  the  process  ID  (PID)  is
               appending  to  the file name specified with the "of=" option
               to create unique file names.
            o  The spawn() facility, used to execute on a  different  node,
               is not implemented on the QNX Operating System at this time.


              Syntax:
                  procs=value      The number of processes to create.


          4.33  Random I/O Offset Alignment "ralign=" Option.

               This option is used when performing  random  I/O,  to  align
          each  random  block offset to a particular alignment, for example
          32K.


              Syntax:
                  ralign=value     The random I/O offset alignment.










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          4.34  Random I/O Data Limit "rlimit=" Option.

               This option is used with random I/O to specify the number of
          bytes  to limit random I/O between (starting from block 0 to this
          range).  This option is independent of the data limit option.


              Syntax:
                  rlimit=value     The random I/O data byte limit.


          4.35  Random Seed Value rseed=" Option.

               This options sets the seed to initialize the  random  number
          generator  with,  when  doing  random I/O.  When selecting random
          I/O, the total statistics displays the random  seed  used  during
          that  test.   This  option  can  be used to repeat the random I/O
          sequence of a test.


              Syntax:
                  rseed=value      The random seed to initialize with.


          4.36  Record Limit "records=" Option.

               This option controls the number of records  to  process  for
          each write and/or read pass of each test.  The "count=" option is
          an alias for this option (supported for dd compatibility).

          Special Notes:
            o  You must specify either a data limit, record limit, or files
               limit  to initiate a test, unless the device type is "disk",
               in which case dt will automatically determine the disk capa-
               city.
            o  When specifying a runtime via  the  "runtime="  option,  the
               record limit controls how many records process for each pass
               (write and/or read pass).
            o  If you specify a infinite  "records=Inf"  value,  each  pass
               will continue until the end of media or file is reached.


              Syntax:
                  records=value    The number of records to process.










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          4.37  Run Time "runtime=" Option.

               This option controls how long the  total  test  should  run.
          When  used in conjunction with a data limit or record limit, mul-
          tiple passes will be performed until the runtime  limit  expires.
          A  later  section entitled "Time_Input_Parameters", describes the
          shorthand notation for time values.

              Syntax:
                  runtime=time     The number of seconds to execute.


          4.38  Record Skip "skip=" Option.

               This option specifies the numer of records to skip prior  to
          starting each write and/or read pass of each test.  The skips are
          accomplished by reading records.

              Syntax:
                  skip=value       The number of records to skip past.


          4.39  Record Seek "seek=" Option.

               This option specifies the number of  records  to  seek  past
          prior  to  starting  each  write and/or read test.  The seeks are
          accomplished by lseek()'ing past records, which  is  much  faster
          than skipping when using random access devices (dd could use this
          option).

              Syntax:
                  seek=value       The number of records to seek past.


          4.40  Data Step "step=" Option.

               This option is used to specify non-sequential  I/O  requests
          to  random  access  devices.  Normally, dt does sequential read &
          writes, but this option specifies that step bytes be seeked  past
          after each request.

              Syntax:
                  step=value       The number of bytes seeked after I/O.


          4.41  Terminal Speed "speed=" Option.

               This option specifies the  terminal  speed  (baud  rate)  to
          setup  prior  to  initiating  the test.  Although dt supports all
          valid baud rates, some speeds may not be supported by all  serial
          line  drivers,  and  in  some cases, specifying higher speeds may



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          result in hardware errors (e.g., silo  overflow,  framing  error,
          and/or  hardware/software  overrun  errors).   The  valid  speeds
          accepted by dt are:

                   0        50        75       110       134       150
                 200       300       600      1200      1800      2400
                4800      9600     19200     38400      57600   115200

          Although a baud rate of zero is accepted, this is done mainly for
          testing  purposes  (some systems use zero to hangup modems).  The
          higher baud rates are only valid  on  systems  which  define  the
          Bxxxxx speeds in termios.h.

          Special Notes:
            o  The default speed is 9600 baud.


              Syntax:
                  speed=value      The tty speed (baud rate) to use.


          4.42  Terminal Read Timeout "timeout=" Option.

               This option specifies the timeout to  use,  in  10ths  of  a
          second,  when  testing  terminal  line  interfaces.   This is the
          timeout used between each character after the first character  is
          received,  which  may prevent tests from hanging when a character
          is garbled and lost.

          Special Notes:
            o  The default terminal timeout is 3 seconds.
            o  The default timeout is automatically adjusted for slow  baud
               rates.


              Syntax:
                  timeout=value    The tty read timeout in .10 seconds.


          4.43  Terminal Read Minimum "ttymin=" Option.

               This option specifies the  minmum  number  of  characers  to
          read, sets the VMIN tty attribute.

          Special Notes:
            o  The tty VMIN field normally gets sets to the  value  of  the
               block size (bs=balue).
            o  Note  that  on  some  systems,  the   VMIN   field   is   an
               unsigned_char, so the maximum value is 255.





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            o  On QNX, this field is an unsigned_short,  so  a  maximum  of
               65535 is valid.


              Syntax:
                  ttymin=value     The tty read minimum count (sets vmin).


          4.44  Enable "enable=" & Disable disable= Options.

               These options are used to either enable or  disable  program
          flags  which  either  alter  default test modes, test actions, or
          provide additional debugging information.  You can specify a sin-
          gle  flag  or  multiple  flags  each  seperated by a comma (e.g.,
          "enable=aio,debug,dump").

              Syntax:
                  enable=flag      Enable one or more of the flags below.
                  disable=flag     Disable one or more of the flags below.

          The flags which can be enabled or disabled are described below.

          4.44.1  POSIX Asynchronous I/O "aio" Flag.