#!/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.
#
############################################################################

#########################
# Function definitions  #
#########################

function usage {
  echo "Usage: $0 [-a] [-d] [-n] [-s <l2s>] <dev>"
  echo "        -a - use asynchronous (buffered) I/O."
  echo "        -d - use direct (non-buffered) I/O."
  echo "        -n - do not verify the data on <dev> before overwriting it."
  echo "        -s - logarithm base two of the I/O size."
  echo "        <dev> - block device to run the I/O performance test on."
}

function drop_caches {
  sync
  echo 3 > /proc/sys/vm/drop_caches
}


#########################
# Default settings      #
#########################

log2_io_size=30       # 1 GB
log2_min_blocksize=12 # 4096 bytes
log2_max_blocksize=26 # 64 MB
iotype=direct
verify_device_data=true


#########################
# Argument processing   #
#########################

set -- $(/usr/bin/getopt "adns:" "$@")
while [ "$1" != "${1#-}" ]
do
  case "$1" in
    '-a') iotype="buffered"; shift;;
    '-d') iotype="direct"; shift;;
    '-n') verify_device_data="false"; shift;;
    '-s') log2_io_size="$2"; shift; shift;;
    '--') shift;;
    *)    usage; exit 1;;
  esac
done

if [ "$#" != 1 ]; then
  usage
  exit 1
fi

device="$1"


####################
# Performance test #
####################

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 [ "${verify_device_data}" = "true" ] \
   && ! cmp -s -n $((2**log2_io_size)) "${device}" /dev/zero
then
  echo "Error: device ${device} still contains data."
  exit 1
fi

if [ "${iotype}" = "direct" ]; then
  dd_oflags="oflag=direct"
  dd_iflags="iflag=direct"
else
  dd_oflags="oflag=sync"
  dd_iflags=""
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
  if [ $log2_blocksize -gt $log2_io_size ]; then
    continue
  fi
  bs=$((2**log2_blocksize))
  count=$((2**(log2_io_size - log2_blocksize)))
  printf "%9d " ${bs}
  for ((i=0;i<3;i++))
  do
    drop_caches
    elapsed="$(dd if=/dev/zero of="${device}" bs=${bs} count=${count} \
                  ${dd_oflags} 2>&1 \
               | sed -n 's/.* \([0-9.]*\) s,.*/\1/p')"
    printf "%8s " "${elapsed}"
  done
  for ((i=0;i<3;i++))
  do
    drop_caches
    elapsed="$(dd if="${device}" of=/dev/null bs=${bs} count=${count} \
                  ${dd_iflags} 2>&1 \
               | sed -n 's/.* \([0-9.]*\) s,.*/\1/p')"
    printf "%8s " "${elapsed}"
  done
  printf "\n"
done