http://qs1969.pair.com?node_id=875723

rizzy has asked for the wisdom of the Perl Monks concerning the following question:

I've been slurping text files into a string using a loop and parsing the text, but I noticed that the memory in windows is always as large as the largest file that has been slurped (i.e., it never drops back down) even if I undefine the string each loop. Is this a problem with windows, or is there a way to resolve this in perl? A (rare) few of the files are 100K+ so this causes problems. I've simplified to code and even in this simple case, the effect is there:

#!C:/Perl/bin -w use File::Listing qw(parse_dir); my $dir='c:/mydir/'; #open the directory and get filenames; opendir(TEMP, $dir) || die("Cannot open directory"); @thefiles= readdir(TEMP); closedir(TEMP); $maxsize=0; #cycle through each of the files; foreach $file (@thefiles) { unless ( ($file eq ".") || ($file eq "..") ) { $filesize = -s $dir.$file; if ($filesize > $maxsize){$maxsize=$filesize} print "$file - $maxsize - $filesize\n"; my $html=''; $slurpfile=$dir.$file; open( my $fh, $slurpfile ) or die "couldn't open\n"; my $html = do { local( $/ ) ; <$fh> } ; undef $html; } }
Basically, I open up the directory and get a list of every file in the directory. Next, each file is individually opened and passed as a string to $html. I immediately undefine the string and repeat the loop. I can't understand why the memory isn't freed up. It should actually be freed up in 3 places each loop, shouldn't it? (1) when I define $html as '' (2) when I slurp the contents of the next file to $html and (3) when I undefine $html.

As it cycles through the thousands of files, I can watch the running maximum filesize and the memory allocated to perl increase in tandem.

I need to slurp the file for various reasons. I wouldn't mind this leak, but I have to do millions of files and it slows things down considerably. Any suggestions?