README

Yngwie
------
 Random I/O Performance Measurement Tool

 Copyright 2011-2012 (c) Felipe Franciosi <felipe@paradoxo.org>

 Disclaimer:
  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.


 Description:
  This program performs read or write operations at random locations
  of a block device and outputs the time (milliseconds) taken for the
  operation to complete.

  The output is in the form: O C B T, where:
   O - Offset where the operation was performed
   C - Number of times the operation was executed
   B - Buffer size
   T - Time (ms) to complete the operation

  The time is printed in milliseconds and includes *only* the time spent
  in the I/O operations.


 Compiling:
  gcc -o yngwie yngwie.c -lrt -Wall -O3 -s


 Usage:
  ./yngwie < -r | -w | -i > < -d dev_name > [ -hysv[v] ] [ -b buf_size ] [ -c count ] [ -o offset ]
 
     One of the following operation modes must be selected:
     -r             Read from device.
     -w             Write to device (*CAUTION* This will overwrite the device).
     -i             Print information about the device (default) to stderr.

     The device must be specified as follows:
     -d <dev_name>  For example: /dev/sdb

     The following options are available for both reading and writing:
     -b <buf_size>  Buffer size, in bytes.
     -c <count>     Repeat the operation <count> times.
     -o <offset>    Offsets <offset> bytes prior to I/O operations.
     -s             Seek back to the offset before the next count.
     -y             Open device with O_SYNC (see open(2) man page).
     -v             Print output of "-i" when reading or writing as well.


 Changelog:
  2011.10.19 - Felipe Franciosi
   - Program creation.

  2011.11.01 - Felipe Franciosi
   - Major modifications.

  2011.12.06 - Felipe Franciosi
   - Include counter option.

  2011.12.19 - Felipe Franciosi
   - Include optional O_SYNC.

  2012.01.16 - Felipe Franciosi
   - Comitting to github. yay!

 TODO:
  add a -B option that buffers all (or most of) the output prior to flushing it
  (useful to prevent disk seeking when outputing to the same device being evaluated)