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Special Forums Hardware Filesystems, Disks and Memory data from blktrace: read speed V.S. write speed Post 302365134 by W.C.C on Monday 26th of October 2009 05:45:15 AM
Old 10-26-2009
data from blktrace: read speed V.S. write speed

I analysed disk performance with blktrace and get some data:
read:
Code:
  8,3    4     2141     2.882115217  3342  Q   R 195732187 + 32 [cat]
  8,3    4     2142     2.882116411  3342  G   R 195732187 + 32 [cat]
  8,3    4     2144     2.882117647  3342  I   R 195732187 + 32 [cat]
  8,3    4     2145     2.882118965  3342  D   R 195732187 + 32 [cat]
  8,3    4     2149     2.884145702     0  C   R 195732187 + 32 [0]

write:
Code:
  
  8,3    4    43622     5.305507398  3436  Q   W 17805895 + 8 [bash]
  8,3    4    43623     5.305508277  3436  G   W 17805895 + 8 [bash]
  8,3    4    43624     5.305508574  3436  I   W 17805895 + 8 [bash]
  8,3    2      414     5.306695591     0  D   W 17805895 + 16 [swapper]
  8,3    2      418     5.307020642     0  C   W 17805895 + 16 [0]

And, d2c time of one read request is 0.002026737s. On the other hand, d2c time of one write request is 0.000325051s. It show: read time > write time. Is it right? why? I have no idea.
 

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mcx convert(1)							  USER COMMANDS 						    mcx convert(1)

  NAME
      mcx convert - convert between mcx storage types

  SYNOPSIS
      mcx convert <matrix-file-in> <matrix-file-out>
      mcx convert [--write-binary] --cone-to-stack <cat-file-in> <cat-file-out>
      mcx convert [--write-binary] --stack-to-cone <cat-file-in> <cat-file-out>

      mcxconvert  is  not  in  actual fact a program. This manual page documents the behaviour and options of the mcx program when invoked in mode
      convert. The options -h, --apropos, --version, -set, --nop, -progress <num> are accessible in all mcx modes. They are described in  the  mcx
      manual page.

      mcx  convert  [--cone-to-stack  (transform  cone	file to stack file)] [--stack-to-cone (transform stack file to cone file)] [--write-binary
      (output native binary format)] [--cat (read and write cat format)] [-cat-max <num> (limit the stack conversion to <num> matrices)]

      In the two-argument invocation without additional arguments, mcx convert converts from the format found in the first file to the other  for-
      mat, i.e.  from native interchange to native binary format or the other way around. When querying with the -q option, mcx{convert} will out-
      put a one-line synopsis describing the matrix in the argument. The --cone-to-stack and --stack-to-cone options convert between the two types
      of concatenated output provided by mclcm.

  DESCRIPTION
      The  mcl	libraries make extensive use of matrices. Matrices are used to encode graphs, matrices and clusterings.  They can be stored either
      in interchange or in binary format. The latter is somewhat more efficient in storage and much faster in both reading and	writing,  but  the
      default is interchange format.

      The  mcl input routines recognize the type of storage they are dealing with. If you want to convert a matrix to the other storage type, sim-
      ply specify the file name of the matrix you want to convert.  mcx convert will recognize its type, and write the	other  type  to  the  file
      specified as the second argument.

  OPTIONS
      --cone-to-stack (transform cone file to stack file)
	This option requires two trailing options, the names of respectively the source cone file and the target stack file.

      --stack-to-cone (transform stack file to cone file)
	This option requires two trailing options, the names of respectively the source stack file and the target cone file.

      --cat (read and write cat format)

      -cat-max <num> (limit the stack conversion to <num> matrices)

      --write-binary (output native binary format)
	This option is only useful with either of the options --cone-to-stack, --stack-to-cone, or --cat.

  AUTHOR
      Stijn van Dongen.

  SEE ALSO
      mcxio(5), and mclfamily(7) for an overview of all the documentation and the utilities in the mcl family.

  mcx convert 12-068						      8 Mar 2012						      mcx convert(1)
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