SPUG: print statement taking ridiculously long

[Thomas Sibley]

On 07/23/2013 10:19 AM, Fred Morris wrote:
> We've got a script. It produces a huge string after much thrashing:
> 
>   $big_string = "60 Megs or so";
> 
> Then it tries to write it to a file:
> 
>   open OUT, ">$file";
>   print OUT $big_string;
>   close OUT;
> 
> Well that print statement takes over half an hour with one core running at 
> 100% CPU! For that matter we've discovered that taking the  length of 
> $big_string takes an inordinate amount of time as well. The job doesn't 
> appear to be swapping.
> 
> This is happening on the Debian build of perl 5.14. It runs (the whole script) 
> in 5 minutes or so on other (older) versions of perl on far more modest 
> hardware.
> 
> Thoughts?

I'd take a look at your disk IO.  (Are you writing to a network FS?  Is
your disk dying?)

tom at whaam ~ $ cat long-string
use strict;
use warnings;

my $big_string = "a" x (60 * 1024**2);

open my $out, ">", "/tmp/big" or die $!;
print { $out } $big_string;
close $out or die $!;

tom at whaam ~ $ perlbrew exec -- time --format "took %es" perl long-string
perl-5.10.1
==========
took 0.20s

perl-5.12.5
==========
took 0.17s

perl-5.14.1
==========
took 0.17s

perl-5.16.3
==========
took 0.16s

perl-5.18
==========
took 0.17s

perl-5.8.3
==========
took 0.19s

perl-5.8.8
==========
took 0.19s