$endtime = time();
$usetime = $endtime - $starttime;
$write_xiaolv = $bytes/$usetime;
$myga_xiaolv = $mygabyte/$usetime;
echo "create 1GB file use time ".$usetime." seconds\n";
echo "speed :".$write_xiaolv." byte/s\n";
echo "speed :".$myga_xiaolv." m/s\n";