Check the hardrive performance of the particular process using a Perl script
in general this script seems to be straight forward.

But here are some suggestions for improvements:

First check for needed command line arguments and die early with a usage message if they are missing/incomplete. Alternatively you could supply defaults for time interval and iterations like this

#stores the time interval
my $time_interval=$ARGV[0] || 10;
#stores the no of iteration
my $test_count=$ARGV[1] || 50;


You also might want to remove the hard coded process name (chrome) and use a third command line parameter

#stores the process name
my $processname=$ARGV[2] || 'chrome';


and

@processes=`iotop -b -n 1 |grep $processname`;


The result of calls to the write method of Spreadsheet::WriteExcel should be checked for success (=0) and failures should be shown somewhere (either on the console and/or in some log file).

The processing of iotop output could be enhanced.


Variables $read and $write are not needed.
Each line needs to be matched only once (while -> if and no need
for matching modifier g)


The regexs could be made more robust and written more readable.


I defined the regex for the throughput part once in a variable ($throughputpattern) and used it twice afterwards in the match. This is a general principle (don't repeat yourself) for better maintainablility.
the regex now uses the x modifier which allows whitespace in the pattern for better spacing and readability (but then you need to express whitespace to be matched explicitly with \s).
I changed the accepted units of B and K to any capital letter. Who knows what throughput might be possible?




   my $throughputpattern = qr{\b (\d+\.\d+) \s+ [A-Z]/s \s+}x;
   foreach(@processes)
   {
      if ($_ =~ /$throughputpattern $throughputpattern/x)
      {
         $read_per_second+=$1;
         $write_per_second+=$2;
      }
   }