dt-usersguide.txt

Linux磁盘测试的源代码,测试磁盘的读写性能

               This flag is used to control use of POSIX  Asynchronous  I/O
          during  testing,  rather  than  the  synchronous  I/O  read() and
          write() system calls.

          Special Notes:
            o  This test mode is only supported on the Tru64 UNIX Operating
               System at this time.
            o  Beware, you may need to rebuild dt on new versions of  Tru64
               Unix due to POSIX changes and/or AIO library changes between
               major releases.
            o  Reference the "aios=" option, for more special notes.


              Flag:
                  aio              POSIX Asynchronous I/O.(Default: disabled)


          4.44.2  Reporting Close Errors "cerror" Flag.

               This flag controls where close errors  are  reported  as  an
          error  or a failure.  When disabled, close errors are reported as
          a warning.  This flag is meant to be used  as  a  workaround  for
          device  drivers which improperly return failures when closing the
          device.  Many system utilities ignore close  failures,  but  when
          testing  terminals and tapes, the close status us very important.
          For example with tapes, the close reflects the status of  writing
          filemarks  (which  also  flush  buffered  data),  and  the rewind



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          status.

              Flag:
                  cerrors          Report close errors.   (Default: enabled)


          4.44.3  Data Comparison "compare" Flag.

               This flag disables data verification during the read pass of
          tests.  This flag should be disabled to read to end of file/media
          to obtain maximum capacity statistics, or to obtain maximum  per-
          formance statistics (less overhead).

              Flag:
                  compare          Data comparison.       (Default: enabled)


          4.44.4  Core Dump on Errors "coredump" Flag.

               This flag controls whether a core  file  is  generated,  via
          abort(),  when dt is exiting with a failure status code.  This is
          mainly used for program debug, and is not  of  much  interest  to
          normal  users.  When testing multiple processes, via fork(), this
          is the only way to debug since the standard dbx debugger can't be
          used  with child processes (this is finally changing in the Tru64
          UNIX V2.0 release, we've waited a long time).

              Flag:
                  coredump         Core dump on errors.   (Default: disabled)


          4.44.5  Diagnostic Logging "diag" Flag.

               This option is only valid  on  Tru64  Unix.   When  enabled,
          error  messages  get  logged to the binary error logger.  This is
          useful to correlate device  error  entries  with  test  failures.
          Please  note,  the  logging only occurs when running as superuser
          (API restriction, not mine!).

              Flag:
                  diag             Log diagnostic msgs.   (Default: disabled)


          4.44.6  Debug Output "debug" Flag.










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          4.44.7  Verbose Debug Output "Debug" Flag.


          4.44.8  Random I/O Debug Output "rdebug" Flag.

               These flags enable two different levels of debug, which  are
          useful  when  trouble-shooting certain problems (i.e., what is dt
          doing to cause this failure?).  Both flags can be  specified  for
          full debug output.

              Flag:
                  debug            Debug output.          (Default: disabled)
                  Debug            Verbose debug output.  (Default: disabled)
                  rdebug           Random debug output.   (Default: disabled)


          4.44.9  Dump Data Buffer "dump" Flag.

               This flag controls dumping of the data  buffer  during  data
          comparision  failures.  If a pattern file is being used, then the
          pattern buffer is also dumped for easy comparision purposes.   To
          prevent  too many bytes from being dumped, esp.  when using large
          block sizes, dumping is limited to 64 bytes of data.

          Special Notes:
            o  When the failure occurs within the first  64  bytes  of  the
               buffer, dumping starts at the beginning of the buffer.
            o  When the failure occurs  at  some  offset  within  the  data
               buffer, then dumping starts at (data limit/2) bytes prior to
               the failing byte to provide context.
            o  The start of the failing data is marked by an asterisk '*'.
            o  You can use the dlimit= option to override the default  dump
               limit.
            o  Buffer addresses are displayed for detection of memory boun-
               dary problems.


              Flag:
                  dump             Dump data buffer.      (Default: enabled)


          4.44.10  Tape EEI Reporting "eei" Flag.

               This option controls the reporting of Extended Error  Infor-
          mation  (EEI) on Tru64 UNIX systems, for tape devices when errors
          occur.  The  standard  tape  information  available  from  mt  is
          reported, along with the EEI status, CAM status, and SCSI request
          sense data.  This is excellent information to help diagnose  tape
          failures. (thank-you John Meneghini!)

              Flag:



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                  eei              Tape EEI reporting.    (Default: enabled)


          4.44.11  Tape Reset Handling "resets" Flag.

               This option is used during SCSI bus and device  reset  test-
          ing,  to  reposition  the tape position (tapes rewind on resets),
          and to continue testing.  This option is only enabled  for  Tru64
          UNIX systems (currently), since this option requires reset detec-
          tion from EEI status, and tape position information from the  CAM
          tape  driver  (although  dt also maintains the tape position as a
          sanity check against the drivers' data).

              Flag:
                  resets           Tape reset handling.   (Default: disabled)


          4.44.12  Flush Terminal I/O Queues "flush" Flag.

               This flag controls  whether  the  terminal  I/O  queues  get
          flushed  before each test begins.  This must be done to ensure no
          residual characters are left in the queues from a prior test,  or
          else data verification errors will be reported.  Residual charac-
          ters may also be left from  a  previous  XOFF'ed  terminal  state
          (output was suspended).

              Flag:
                  flush            Flush tty I/O queues.  (Default: enabled)


          4.44.13  Log File Header "header" Flag.

               When a log file is specified, dt  automatically  writes  the
          command  line  and dt version information at the beginning of the
          log file.  This option allows you to control whether this  header
          should be written.

              Flag:
                  header           Log file header.       (Default: enabled)


          4.44.14  Logical Block Data Mode "lbdata" Flag.

               This option enables a  feature  called  logical  block  data
          mode.   This  feature allows reading/writing of a 4-byte (32-bit)
          logical block address at the beginning of each data block tested.
          The block number is stored using SCSI byte ordering (big-endian),
          which matches what the SCSI Write Same w/lbdata option  uses,  so
          dt  can verify this pattern, generated by scu's "write same" com-
          mand.




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          Special Notes:
            o  The starting logical block address  defaults  to  0,  unless
               overridden with the "lba=" option.
            o  The logical block size defaults to 512 bytes,  unless  over-
               ridden with the "lbs=" option.
            o  The logical block address is always inserted started at  the
               beginning of each data block (record).
            o  Enabling this feature will  degrade  performance  statistics
               (slightly).


          4.44.15  Enable Loopback Mode "loopback" Flag.

               This flag specifies that either the  input  or  output  file
          should be used in a loopback mode.  In loopback mode, dt forks(),
          and makes the child process the reader, while the parent  process
          becomes  the  writer.   In  previous  versions  of dt, you had to
          specify both the same input and output file  to  enable  loopback
          mode.  When specifying this flag, dt automatically duplicates the
          input or output device, which is a little cleaner  than  the  old
          method (which still works).

               Some people may argue that dt  should  automatically  enable
          loopback  mode when a single terminal or FIFO device is detected.
          The rationale behind not doing this is described below:
          1.   You may wish to have another process as reader and/or writer
               (which also includes another program, not necessarily dt).
          2.   You may wish to perform device loopback between two  systems
               (e.g.,  to verify the terminal drivers of two operating sys-
               tems are compatible).
          3.   A goal of dt is not to force (hardcode) actions  or  options
               to  make  the  program more flexible.  A minimum of validity
               checking is done to avoid being  too  restrictive,  although
               hooks exists to do this.


          Special Notes:
            o  The read verify flag is automatically disabled.
            o  This mode is most useful with terminal devices and/or FIFO's
               (named pipes).


          4.44.16  Microsecond Delays "microdelay" Flag.

               This flag tells dt that delay  values,  i.e.  "sdelay="  and
          others,  should  be  executed using microsecond intervals, rather
          the second intervals.  (thank-you George Bittner for implementing
          this support!)

              Flag:
                  microdelay       Microsecond delays.    (Default: disabled)



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          4.44.17  Memory Mapped I/O "mmap" Flag.

               This flag controls whether the memory mapped API is used for
          testing.   This test mode is currently supported on SUN/OS, Tru64
          UNIX, and Linux operating systems.

          Special Notes:
            o  The block size specified "bs=" must be  a  multiple  of  the
               system dependent page size (normally 4k or 8k).
            o  An msync() is done after writing and  prior  to  closing  to
               force modified pages to permanent storage.  It may be useful
               to add an option to inhibit this action at some  point,  but
               my testing was specifically to time mmap performance.  Obvi-
               ously, invalidating the memory mapped pages, kind of defeats
               the purpose of using memory mapped files in the first place.
            o  Specifying multiple passes when doing a  read  verify  test,
               gives you a good indication of the system paging utilization
               on successive passes.
            o  Memory mapping large data files (many megabytes) may exhaust
               certain  system  resources.   On  an early version of SUN/OS
               V4.0?, I could hang my system by gobbling up all of physical
               memory  and  forcing  paging (this was certainly a bug which
               has probably been corrected since then).


              Flag:
                  mmap             Memory mapped I/O.     (Default: disabled)


          4.44.18  Test Modem Lines "modem" Flag.

               This flag controls the  testing  of  terminal  modem  lines.
          Normally,  dt  disables  modem  control,  via  setting CLOCAL, to
          prevent tests from  hanging.   When  this  flag  is  enabled,  dt
          enables  modem  control, via clearing CLOCAL, and then monitoring
          the modem signals looking  for  either  carrier  detect  (CD)  or
          dataset ready (DSR) before allowing the