[issue43911] Queue.get() memory leak

[Jens]

Jens <multiks2200 at gmail.com> added the comment:

Thanks for your input.

So i've run the tests with the List of Lists Queue class, there seems to be a resulting difference depending on what qsize() method I define, that is called my script.

For an instance where qsize just return None,

	class QueueLists(list):

	    def put(self, x):
		if not self or len(self[-1]) >= 66:
		    self.append([])
		self[-1].append(x)

	    def get(self):
		if not self:
		    raise IndexError
		block = self[0]
		x = block.pop(0)
		if not block:
		    self.pop(0)
		return x

	    # def qsize(self):
	    #     tot = 0
	    #     for elem in self:
	    #         tot += len(elem)
	    #     return tot

	    def qsize(self):
		return None

The results are:
>#########
>del_after_puts False del_after_gets True n_puts 20000000
>before run
>mem_pct 0.15%
>------ put done  ----- qsize None
>mem_pct 38.06% 
>------ gets done  ----- qsize None
>mem_pct 2.35% 
>deleting queue after gets []
>mem_pct 2.35% 
>time elapsed 0:01:04.703969

For a Queue instance, where qsize() returns the actual size

	class QueueLists(list):

	    def put(self, x):
		if not self or len(self[-1]) >= 66:
		    self.append([])
		self[-1].append(x)

	    def get(self):
		if not self:
		    raise IndexError
		block = self[0]
		x = block.pop(0)
		if not block:
		    self.pop(0)
		return x

	    def qsize(self):
		tot = 0
		for elem in self:
		    tot += len(elem)
		return tot
the results are:

>#########
>del_after_puts False del_after_gets True n_puts 20000000
>before run
>mem_pct 0.15% 
>------ put done  ----- qsize 20000000
>mem_pct 38.05% 
>------ gets done  ----- qsize 0
>mem_pct 2.35% 
>deleting queue after gets []
>mem_pct 0.18% 
>time elapsed 0:00:53.347746

So both instances leak as you've indicated, but the one that returns None as queue size does not get it's leak released after the instance is deleted which is a weird difference.

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue43911>
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