memory leak

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

i'm pretty certain i have a memory leak - its footprint grows steadily until it dies

i have tried putting

find_cycle($obj);
[download]

on all suspect objects in my code, but it is not reporting anything. does this mean these objects definitely do not have circular references?

i pass by ref everywhere, once a sub goes out of scope it's reference should go away, is that correct?

EDIT:
Edited this to say I have searched perlmonks and now i think maybe my memory is just growing and not leaking. Here's an example:

--------------------------------

package Obj;

sub new 
{
    my $class = shift; 
    my $name = shift;
    my $value = shift;
    
    my $self = {
        NAME => $obj, 
        VALUE => $value 
    };

    bless $self, $class;
    
    return $self;
}

return 1;




--------------------------------
# main.pl
--------------------------------

my @objects = ();
my $i = 0;

while($i < 20000000) {
    @objects = getObjects(); 

        # do something

    $i += 100;
}

sub getObjects
{
    my @objects = ();
    my $object = undef;
    my %ht = ();  # say i use a hash somewhere in here
    my $i = 0;

    
    for($i=0; $i<100; $i++) {
        $object = new Obj("name_$i", $i);
        $objects[$i] = $object 
    }
    
    return @objects;
}
[download]

Will the array of 100 objects and hash in the sub GetObjs be reclaimed/re-used or will another chunk of memory for 100 objects be taken every call to this sub?

EDIT 2

i think i found the issue? let's say getObjects opened and closed a db connection every call to get its data, using Win32::ODBC. This appears to be causing the memory to grow. here is an example:

use Win32::ODBC; 

my @objects = (); 
my $i = 0; 

while($i < 20000000) { 
    @objects = getObjects(); 
    # do something 
    $i += 100; 
} 

sub getObjects { 
    my @objects = (); 
    my $object = undef; 
    my $db = undef; 
    my $i = 0; 
    
    $db = new Win32::ODBC("DSN=dsnname;UID=username;PWD=pw%") || die; 
    
    for($i=0; $i<100; $i++) { 
        #$object = new Obj("name_$i", $i); 
        $objects[$i] = $object 
    } 
    
    if($db) { 
        $db->Close(); 
    }
    
    return @objects; 

}
[download]

I tried adding $db = undef; with no luck. does $db not get re-used every call??

Comment on memory leak Select or Download Code

Replies are listed 'Best First'.
Re: memory leak by alexlc (Beadle) on Aug 26, 2009 at 01:10 UTC
Will the array of 100 objects and hash in the sub GetObjs be reclaimed/re-used or will another chunk of memory for 100 objects be taken every call to this sub? Yes. Once there are no longer any references to a variable ( as would happen to @objects, $object, %ht ) they will be destroyed. This won't give the memory back to the OS, but perl will re-use it internally. If you aren't using them, you should be using 'strict' and probably 'warnings' because it may point out places where you are accidentally using a global variable where you didn't mean to. The code you posted doesn't run out of memory for me. -- AlexLC	[reply]
Re^2: memory leak by bob_dobalina (Sexton) on Aug 26, 2009 at 03:31 UTC
thanks for the reply. i am using strict and warnings. i really try to avoid globals; this example is the only place i could see really eating up memory. how about this: assuming the same code, say you took each object and passed it around: `while($i < 20000000) { @objects = getObjects(); foreach my $obj (@objects) { SomeMethod($obj); } $i += 100; } sub SomeMethod { my $obj = shift; AnotherMethod($obj); } sub AnotherMethod { my $obj = shift; }` [download] Isn't the $obj param essentialy a hash ref? This doesn't increment the reference count in every sub does it? It should all be one reference to the same memory location, right? Or - what if the object had a "member" that was a ref to an array of other objects, could that cause problems?: `-------------------------------- package Obj; sub new { my $class = shift; my $name = shift; my $arrayRef = shift; my $self = { NAME => $obj, ARRAY_REF => $arrayRef }; bless $self, $class; return $self; } return 1; # ex: my $obj = new Obj("x", \@arrayOfObjects);` [download]	[reply] [d/l] [select]
Re: memory leak by BioLion (Curate) on Aug 26, 2009 at 08:34 UTC
To be really sure you are not leaking memory, check out Devel::Leak. Just a something something...	[reply]
Re^2: memory leak by bob_dobalina (Sexton) on Aug 26, 2009 at 16:01 UTC
I put Devel::Leak in my outer loop and am not quite sure what I'm looking at - most loops it does this: `old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0` [download] but every say 5 iterations it does this: ew 04EF14D4 : new 04EF14E0 : new 04EF1510 : new 04EF1558 : new 04EF15E +8 : new 04EF16B4 : new 04EF17E0 : new 04EF17F8 : new 04EF184C : new 0 +4EF1858 : new 04EF18A0 : new 04EF1CB4 : new 04EF1CD8 : new 04EF1FF0 : + new 04EF214C : new 04EF21C4 : new 04EF21E8 : new 04EEA73C : new 04EE +A748 : new 04EEA760 : new 04EEA8BC : new 04EEAA3C : new 04EEAA9C : ne +w 04EEAAC0 : new 04EEAB50 : new 04EEABBC : new 04EEACA0 : new 04EEACB +8 : new 04EEAD90 : new 04EEAF1C : new 04EEAFE8 : new 04EEB0CC : new 0 +4EEB138 : new 04EEB21C : new 04EEB228 : new 04EEB234 : new 04EEB240 : + new 04EEB2D0 : new 04EEB378 : new 04EEB3D8 : new 04EEB3E4 : new 04EE +B480 : new 04EE38BC : new 04EE394C : new 04EE3970 : new 04EE39B8 : ne +w 04EE3B50 : new 04EE3DE4 : new 04EE3DFC : new 04EE3EC8 : new 04EE3EE +0 : new 04EE3FAC : new 04EE4018 : new 04EE40C0 : new 04EE4120 : new 0 +4EE41E0 : new 04EE4534 : new 04EE45F4 : new 04EE46F0 : new 04EE4744 : + new 04EDCC7C : new 04EDCEA4 : new 04EDCEF8 : new 04EDCF28 : new 04ED +D528 : new 04EDD690 : new 04EDD6CC : new 04EDD708 : new 04EDD930 : ne +w 04EDD948 : new 04ED6190 : new 04ED61C0 : new 04ED6460 : new 04ED648 +4 : new 04ED6688 : new 04ED66A0 : new 04ED66D0 : new 04ED66F4 : new 0 +4ED6868 : new 04ED69D0 : new 04ED6A54 : new 04ED6B14 : new 04ED6B8C : + new 04ECF238 : new 04ECF364 : new 04ECF5A4 : new 04ECF6AC : new 04EC +F700 : new 04ECF994 : new 04ECFB20 : new 04EFF644 : new 04EF850C : ne +w 04EF87AC : new 04EF8D70 : new 04EF8D88 : new 04EF18F4 : new 04EF1A7 +4 : new 04EF1DEC : new 04EF2338 : new 04EEA700 : new 04EEAD48 : new 0 +4EEAE08 : new 04EEAE2C : new 04EEB234 : new 04EEB2E8 : new 04EE3C64 : + new 04EE3D90 : new 04EE42C4 : new 04EE454C : new 04EE46D8 : new 04ED +69AC : new 04F064F8 : new 04EFF008 : new 04EFF344 : new 04EFF854 : ne +w 04EFFE60 : new 04EF83C8 : new 04EF84D0 : new 04EF87AC : new 04EF881 +8 : new 04EF181C : new 04EF1894 : new 04EF18D0 : new 04EF1A20 : new 0 +4EEA994 : new 04EEB15C : new 04EEB180 : new 04EEB4F8 : new 04EE4294 : + new 04EE46FC : new 04EDCEE0 : new 04ED5E60 : new 04F0D36C : new 04F0 +6744 : new 04EFF008 : new 04EFF44C : new 04EFF6EC : new 04EFF794 : ne +w 04EFFB54 : new 04EFFCE0 : new 04EF8524 : new 04EF87E8 : new 04EF1C3 +C : new 04EF1D38 : ... etc .... old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 old (1): 0 [download] Any insight would be appreciated!	[reply] [d/l] [select]
Re^3: memory leak by BioLion (Curate) on Aug 26, 2009 at 18:58 UTC
Hmmm. Looking around though I think the problem may be how your version of perl is compiled (you need the debugging flags set). There are other threads where people have similar issues understanding devel::leak Making Devel::Leak useful also there is some good advice in Re: Memory Leak HTH Just a something something...	[reply]
Re^4: memory leak by bob_dobalina (Sexton) on Aug 26, 2009 at 20:08 UTC
Re^5: memory leak by BioLion (Curate) on Aug 27, 2009 at 10:55 UTC