#!/bin/bash

trap 'killall -9 parallel-dd' INT

tmpdir=$1

usage="USAGE: parallel-dd TMPDIR\n"

[ -z $tmpdir ] && printf "$usage" && exit

mkdir $tmpdir

size=12K

serial_dd() {
    local thread=$1
    mkdir -p ${tmpdir}/$thread
    # create 10000 files per thread (hence total of 1 million files)
    for count in {1..10000}
    do
        local uuidfile=`uuidgen`
        local part1=`expr substr $uuidfile 1 2`
        local part2=`expr substr $uuidfile 3 2`

        echo $((time (mkdir -p ${tmpdir}/$part1/$part2;  dd if=/dev/zero of=${tmpdir}/$part1/$part2/$uuidfile bs=${size} count=1 oflag=direct conv=fdatasync ) 2>&1 ) | grep real | sed -e 's/real//' | tr -d '\t')
    done
}

parallel_dd() {
    for i in {1..100}
    do
        serial_dd $i &
        pids[${i}]=$!
    done

    for pid in ${pids[*]}; do
        wait $pid
    done
    echo -n "Total time: "
}

for milCount in {1..30}
do
    echo ----------
    ((time parallel_dd) 2>&1)
    echo Finished run ${milCount}
done