Memory usage of Perl script

Question

I have a Perl script, fetch url like http://1.1.1.1/1.jpg from MySQL using DBI, and download this jpg file using LWP::Simple. It's a infinite loop.

while (1) {
    my $url=&fetch_url_from_mysql;
    if ($url){        
        &download_jpg($url);
    } else {
        sleep 1;
    }
}

Plain simple. I suppose the memory usage would be stay in certain amount. But after one month of continuous running of this script. The memory usage is 7.5G!

How can I profile it?

Is fetch_url_from_mysql opening a new connection every time, and not closing it? — vegadoom
– vegadoom, Commented Mar 30, 2012 at 5:56
Yes. I call DBI::connect before while loop, in fetch_url_from_mysql is prepare,execute,fetch and return $url — everbox
– everbox, Commented Mar 30, 2012 at 6:05
In washing your code down to a clean example you washed away the parts that actually use memory. — DavidO
– DavidO, Commented Mar 30, 2012 at 6:12

Community · Accepted Answer · 2017-05-23 12:04:29Z

1

For profiling, set an explitict exit. Create a counter, and exit from your program if your iteration is equal or bigger than this.

For profiling, use NYTprof:

perl -d:NYTProf script.pl nytprofhtml

But you are dealing with a memory leak here.

Read this to find a memory leak: How can I find memory leaks in long-running Perl program?

Most probably you have a variable that will never be freed. Perl frees memory if a variable goes out of scope, but one of your variables never goes out of scope.

Use $variable=undef to free up the memory.

If you port your whole script maybe we could find a leak in it.

regards,

edited May 23, 2017 at 12:04

CommunityBot

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answered Mar 30, 2012 at 10:56

user1126070

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