[PyQt] Is PyQt really freeing memory?

[Albert Cervera i Areny]

A Dimarts, 11 d'agost de 2009, Phil Thompson va escriure:
> On Sun, 2 Aug 2009 02:12:52 +0200, Albert Cervera i Areny
>
> <albert at nan-tic.com> wrote:
> > I've been having problems with my application consuming too much memory
> > after
> > some time running and today decided to take a deeper look. I've ended up
> > with
> > the attach test.py script which either demonstrates PyQt is not freeing
> > memory
> > appropiately when signals are involved or I simply don't understand how
> > this
> > works.
> >
> > As you can see the script creates lists with 100.000 QObjects and prints
> > the
> > memory used. As python won't free memory but reuse what has already been
> > freed
> > I expect a call like:
> >
> > list = []
> > fill in the list with lots of data
> >
> > to take as much memory as:
> >
> > list = []
> > fill in the list with lots of data
> > list = []
> > fill in the list with the same lots of data
> >
> > If you give it a try, you'll realize that this is true if you create
> > 100.000
> > objects with no signal connections. But if you connect and disconnect  a
> > signal for those objects, the memory used after the second fill is larger
> > than
> > after the first one.
> >
> > It seems to me that some data is being leaked in connect() and
>
> disconnect()
>
> > functions (which, by the way, take up a lot of memory).
> >
> > Here's the output of the script in my system:
> >
> > $ python test.py one no
> > Executing 'one' without signals
> > Memory:  21564
> >
> > $ python test.py one yes
> > Executing 'one' with signals
> > Memory:  64992
> >
> > $ python test.py two yes
> > Executing 'two' with signals
> > Memory:  125592
> >
> > $ python test.py two+remove yes
> > Executing 'two+remove' with signals
> > Memory:  93880
> >
> > $ python test.py three+remove yes
> > Executing 'three+remove' with signals
> > Memory:  122808
> >
> > So "two+remove yes" should be using 64992 Kb (just like "one yes") but it
> > uses
> > 50% more. The same happens with "three+remove yes", again more 30 Mb!
>
> The proxies that are created to allow Python callables to be used as Qt
> slots are destroyed using QObject::deleteLater(). As your example doesn't
> have an event loop they never get destroyed.
>
> In tonight's snapshot I've changed the implementation so they get destroyed
> immediately as it does simplify the code a little.

Thank you very much. By the way, is there a reason why creating 100.000 
objects uses only 21564 Kb and connecting them to a slot uses 64992 Kb. It 
seems a lot of memory for "just" connecting signals...

>
> Phil


-- 
Albert Cervera i Areny
http://www.NaN-tic.com
Mòbil: +34 669 40 40 18