Bug #48781 [Asn]: Cyclical garbage collector memory leak

Edit report at http://bugs.php.net/bug.php?id=48781&edit=1

 ID:               48781
 Updated by:       [email protected]
 Reported by:      nate at frickenate dot com
 Summary:          Cyclical garbage collector memory leak
 Status:           Assigned
 Type:             Bug
 Package:          Scripting Engine problem
 Operating System: Debian 5.0 kernel 2.6.24-23-xen
 PHP Version:      5.3.0
 Assigned To:      dmitry

 New Comment:

Yeah. I confirm the problem. It looks like on each 100,000 iterations
PHP runs GC about 12 times. And on each GC run it looses 2 objects
referenced by $user. I'll try to fix it.


Previous Comments:
------------------------------------------------------------------------
[2010-04-18 02:28:35] [email protected]

I am unable to duplicate this behaviour using 5.3.2. The code given
below consistently uses 0.65 MB even up to 10 million iterations - I
pasted the output of up to 6 million, with the extended GC reporting
turned on:

<?php

class User {
    protected $profile;

    public function __construct () {
        $this->profile = new UserProfile($this);
    }
    
    public function dispose() {
		$this->profile->dispose();
		$this->profile = null;
    }
}

class UserProfile {
    private $user;

    public function __construct ($user) {
        $this->user = $user;
    }
    
    public function dispose() {
		$this->user = null;
    }
}

for ($userid = 1; ; $userid++) {
	if(isset($user)) {
		$user->dispose();
	}
    $user = new User;

    if ($userid % 100000 == 0)
        printf("memory usage after %s users: %s MB.\n",
number_format($userid), number_format(memory_get_usage() / 1024 / 1024,
2));

    continue;
}

?>


memory usage after 100,000 users: 0.65 MB.
memory usage after 200,000 users: 0.65 MB.
memory usage after 300,000 users: 0.65 MB.

[snip]

memory usage after 5,700,000 users: 0.65 MB.
memory usage after 5,800,000 users: 0.65 MB.
memory usage after 5,900,000 users: 0.65 MB.

GC Statistics
-------------
Runs:               0
Collected:          0
Root buffer length: 0
Root buffer peak:   9

      Possible            Remove from  Marked
        Root    Buffered     buffer     grey
      --------  --------  -----------  ------
ZVAL        16         7          7         0
ZOBJ  77999984  11999998   11999998         0

------------------------------------------------------------------------
[2010-01-05 19:31:01] nightstorm at tlen dot pl

I confirm, there is a true memory leak. Consider the following script,
where the references are unmounted manually with an extra dispose()
method:

~~~~
<?php

/*
How to use:
    a) run test 1 by running code as-is
    b) run test 2 by commenting out test 1, uncomment test 2
    c) run test 3 by commenting out test 1 & 2, uncomment test 3
*/

class User {
    protected
        $profile;

    public function __construct () {
        $this->profile = new UserProfile($this);
    }
    
    public function dispose()
    {
		$this->profile->dispose();
		$this->profile = null;
    } // end dispose();
}

class UserProfile {
    private
        $user;

    public function __construct ($user) {
        $this->user = $user;
    }
    
    public function dispose()
    {
		$this->user = null;
    } // end dispose();
}

for ($userid = 1; ; $userid++) {
	if(isset($user))
	{
		$user->dispose();
	}
    $user = new User;

    if ($userid % 100000 == 0)
        printf("memory usage after %s users: %s MB.\n",
number_format($userid), number_format(memory_get_usage() / 1024 / 1024,
2));

    continue;
}
~~~~~

In this case the result is still the same (PHP 5.3.1):

~~~~
memory usage after 100,000 users: 0.61 MB.
memory usage after 200,000 users: 0.61 MB.
memory usage after 300,000 users: 0.61 MB.
memory usage after 400,000 users: 0.61 MB.
memory usage after 500,000 users: 0.61 MB.
memory usage after 600,000 users: 0.61 MB.
memory usage after 700,000 users: 0.61 MB.
memory usage after 800,000 users: 0.61 MB.
memory usage after 900,000 users: 0.61 MB.
memory usage after 1,000,000 users: 0.61 MB.
memory usage after 1,100,000 users: 0.61 MB.
memory usage after 1,200,000 users: 0.61 MB.
~~~~

If we enable the garbage collector and remove the dispose() method, the
used memory level begins to increase, and if we call gc_collect_cycles()
after creating a new object, the used memory increases even much faster.
On my PC, it is not able to perform display even a single control
message after 100000 iterations. It stopped after approx. 33000 users:

~~~~
memory usage after 30,000 users: 25.37 MB.
memory usage after 31,000 users: 26.07 MB.
memory usage after 32,000 users: 26.76 MB.
memory usage after 33,000 users: 31.46 MB.

Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to
allocate 89 bytes) in /home/me/test/memleak.php on line 17
~~~~

------------------------------------------------------------------------
[2009-12-15 01:00:00] php-bugs at lists dot php dot net

No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".

------------------------------------------------------------------------
[2009-12-08 15:23:16] nate at frickenate dot com

No change, same problem. Considering this bug hasn't even been looked at
or assigned, no surprise there.

------------------------------------------------------------------------
[2009-12-07 09:12:35] [email protected]

Please try using this snapshot:

  http://snaps.php.net/php5.3-latest.tar.gz
 
For Windows:

  http://windows.php.net/snapshots/



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


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