Perl performance when reading and writing the same file - perl

Question

Is there any noticeable performance difference between these two ways of reading/writing a user file with Perl, on Linux?
Option 1:
open (READFILE, '<:utf8', "users/$_[0]") or die ("no read users/$_[0]");
# Do the reading
close (READFILE) or die;
# Do more stuff
open (WRITEFILE, '>:utf8', "users/$_[0]") or die ("no write users/$_[0]"); flock (WRITEFILE, 2) or die ("no lock users/$_[0]");
# Do the writing
close (WRITEFILE) or die;
Option 2:
open (USERFILE, '+<:utf8', "users/$_[0]") or die ("no open users/$_[0]"); flock (USERFILE, 2) or die ("no lock users/$_[0]");
# Do the reading
# Do more stuff
seek (USERFILE, 0, 0); truncate (USERFILE, 0);
# Do the writing
close (USERFILE) or die ("no write users/$_[0]");
The user files are not big, typically 20-40 lines or 2-4 KB each.
And would there be other reasons for choosing option 1 or 2 (or a 3rd option)?

Answer 1

Here is a benchmark which you can use to test it, I suspect that getting a new file descriptor is the part that takes longer if you close and then open again.
#!/usr/bin/env perl
use warnings;
use strict;
use open qw(:encoding(utf8) :std);
use Benchmark qw<cmpthese>;
my $text = <<TEXT;
I had some longer text here, but for better readability, just
these two lines.
TEXT
cmpthese(10_000,{
close => sub{
open my $file, '<',"bla" or die "$!";
my #array = <$file>;
close $file or die;
open $file, '>',"bla" or die "$!";
$file->print($text)
},
truncate => sub {
open my $file, '+<',"bla" or die "$!";
my #array = <$file>;
seek $file,0,0;
truncate $file, 0;
$file->print($text)
},
truncate_flock => sub {
open my $file, '+<',"bla" or die "$!";
flock $file, 2;
my #array = <$file>;
seek $file,0,0;
truncate $file, 0;
$file->print($text)
},
});
Output on my machine:
Rate close truncate_flock truncate
close 2703/s -- -15% -17%
truncate_flock 3175/s 17% -- -3%
truncate 3257/s 21% 3% --
A higher rate is better. Using close is 1.17 times slower.
But it heavily depends on how long your more stuff takes, since you're flocking the file in your truncate example and if another program is trying to access this file it may be slowed down because of that.