#!/bin/bash

############################################################################
#
# Script for testing block device I/O performance. Running this script on a
# block device that is connected to a remote SCST target device allows to
# test the performance of the transport protocols implemented in SCST. The
# operation of this script is similar to iozone, while this script is easier
# to use.
#
# Copyright (C) 2009 Bart Van Assche <bart.vanassche@gmail.com>.
#
# 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, version 2
# of the License.
#
# 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.
#
############################################################################

device="$1"
log2_io_size=31       # 2 GB
log2_min_blocksize=12 # 4096 bytes
log2_max_blocksize=26 # 64 MB

if [ ! -e "${device}" ]; then
  echo "Error: device ${device} does not exist."
  exit 1
fi

if [ ! -w "${device}" ]; then
  echo "Error: device ${device} is not writeable."
  exit 1
fi

if ! cmp -s -n $((2**log2_io_size)) "${device}" /dev/zero; then
  echo "Error: device ${device} still contains data."
  exit 1
fi

printf "%9s %8s %8s %8s %8s %8s %8s\n" blocksize W W W R R R

for ((log2_blocksize = log2_max_blocksize; log2_blocksize >= log2_min_blocksize; log2_blocksize--))
do
  bs=$((2**log2_blocksize))
  printf "%9d " ${bs}
  for ((i=0;i<3;i++))
  do
    elapsed="$(dd if=/dev/zero of="${device}" bs=${bs} oflag=direct 2>&1 \
               | sed -n 's/.* \([0-9.]*\) s,.*/\1/p')"
    printf "%8s " "${elapsed}"
  done
  for ((i=0;i<3;i++))
  do
    elapsed="$(dd if="${device}" of=/dev/null bs=${bs} iflag=direct 2>&1 \
               | sed -n 's/.* \([0-9.]*\) s,.*/\1/p')"
    printf "%8s " "${elapsed}"
  done
  printf "\n"
done