[Paraview-developers] garbage collection revisited (hijacked thread)

[Berk Geveci]

Hi John,

I started removing from some places where it is not necessary.
vtkDataObject and subclasses for example. It hasn't made it to master yet
but it will before VTK 6.0. Any other place where it is not absolutely
necessary, we should take it out. This should leave a few places including
some rendering classes and pipeline connectivity (i.e. setting input to
filters). That one is very hard to get rid of. Impossible without changing
the API significantly. However, there are other ways of executing a filter
without setting the input so we may be able to live with it. I CC'ed VTK
developers since this is a broader VTK discussion. How do folks feel about
garbage collection?

-berk


On Mon, Mar 4, 2013 at 4:18 AM, Biddiscombe, John A. <biddisco at cscs.ch>wrote:

>  Utkarsh - sorry for hijacking this tread. (Well, actually I’m not sorry,
> but I have to say that out of politeness)****
>
> ** **
>
> I have some big problems with the garbage collection. The main problem is
> that it simply isn’t needed in 99.9% of the code in vtk/paraview, but
> unfortunately is used throughout. There are some actor/mapper/renderer
> places where it is useful, but everywhere else it is a huge waste of
> resources/time.****
>
> I have some structures like a SIL populated with a tree of several
> thousand objects, it takes minutes to delete (when debugging is enabled for
> sure) (and construction is slower than necessary). In my own code, I have
> had to resort to replacing all calls to Delete with FastDelete and never
> yet had any problem with dangling references or double deletion. I am
> considering modifying the pv source in places like the SIL to also use
> fastdelete.****
>
> ** **
>
> Could we consider Making non garbage collection/deletion the default, and
> only using it in places where we know circular reference loops are likely?
> ****
>
> ** **
>
> JB****
>
> ** **
>
> *From:* paraview-developers-bounces at paraview.org [mailto:
> paraview-developers-bounces at paraview.org] *On Behalf Of *Utkarsh Ayachit
> *Sent:* 03 March 2013 17:21
> *To:* Joshua Murphy
> *Cc:* paraview-developers at paraview.org
> *Subject:* Re: [Paraview-developers] how do I force garbage collection?***
> *
>
> ** **
>
> Josh,****
>
> ** **
>
> I am sending you a patch is a separate email. Just to summarize for the
> list:****
>
> ** **
>
> - When writing plugins/readers, turn on CMake flag VTK_DEBUG_LEAKS.
> ParaView will start dumping messages about any VTK objects that are not
> cleaned up while exiting the application. That helps to catch stray
> VTK-object references early in the development process.****
>
> ** **
>
> -  Use vtkNew<> for creating local VTK objects in methods. Developers
> often forget to call the Delete() before exiting the method esp. when
> complicated if/else/swicthes are involved.****
>
> ** **
>
> - Use vtkSmartPointer<> or vtkWeakPointer<> when storing vtkObjects in STL
> maps/list. Makes memory management a lot easier.****
>
> ** **
>
> Utkarsh****
>
> ** **
>
> On Fri, Feb 22, 2013 at 3:27 PM, Utkarsh Ayachit <
> utkarsh.ayachit at kitware.com> wrote:****
>
> Josh,****
>
> ** **
>
> VTK/ParaView uses reference counting. So as long as a there's a reference
> held to any dataobject, Delete() is not going to release it. Barring
> cycles, a quick way to see if Delete() will result in clearing the object,
> is to look it it's ReferenceCount member variable before calling Delete().
> However if you're passing the data allocated as output from your filters
> then the reference maybe getting held by the pipeline beyond your control.
> If you can share the code, I can see if I can explain why the memory may
> not be getting released.****
>
> ** **
>
> Utkarsh****
>
> ** **
>
> On Fri, Feb 22, 2013 at 12:22 PM, Joshua Murphy <
> Joshua.Murphy at lasp.colorado.edu> wrote:****
>
>   Hello,****
>
> ** **
>
> I am writing a cache system for my reader, and I am trying to figure out
> how to force a garbage collection after I dump my cache.****
>
> ** **
>
> Does anyone know how to force ParaView to collect garbage?  Currently
> after I purge my cache (I am calling Delete() on all of the objects and
> destroying the remainder of the cache map) the system memory does not free
> up… ParaView remains in control of all of the memory for the dumped cache
> items, and when the new cache is introduced, the memory usage just keeps
> going up.****
>
> ** **
>
> I suppose it is possible that I am missing some fundamental understanding
> of how ParaView and VTK manage memory, so if someone could help that would
> be great.****
>
> ** **
>
> ** **
>
> Thanks,****
>
> ** **
>
> Josh****
>
> ** **
>
> ****
>
> Joshua J. Murphy****
>
> Computer Scientist****
>
> Laboratory for Atmospheric and Space Physics****
>
> University of Colorado, Boulder****
>
> ** **
>
> ** **
>
> _______________________________________________
> Paraview-developers mailing list
> Paraview-developers at paraview.org
> http://public.kitware.com/mailman/listinfo/paraview-developers****
>
>  ** **
>
> ** **
>
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>
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