Re: problem with first use of a copied pipeline layer texture not freeing, subsequent textures do free

[Lionel Landwerlin <llandwerlin gmail com>]

Hi Reza,

It seems that the backend will keep a reference to the last pipeline
used :

https://git.gnome.org/browse/cogl/tree/cogl/driver/gl/cogl-pipeline-ope
ngl.c#n1390

My understanding is that this is done to limit the amount of state that
needs to be flushed onto the driver for every pipeline you draw with.

I suppose if you draw one more time with a different pipeline, it would
get rid of that reference and dispose the texture attached to it.

As far as I know, pipelines are not immutable. Although you might want
to pretend they are for example if you are deriving for a complex
pipeline with many copies on which you just change one property. 

Cheers,

-
Lionel

On Mon, 2016-04-18 at 16:22 -0700, Reza Ghassemi wrote:
> Hi,
> I'm cc'ing this question to the clutter  mailing list because the
> cogl mailing list has very little traffic
> ----
>
> I am either using pipelines incorrectly or found a problem in cogl
> pipeline
> layer code.  Are they really supposed to be treated as immutable
> after
> you've rendered with them?  I just read that in check-in comments and
> that
> is not how I programmed my code.  In this problem case I'm not making
> a
> change after rendering so the immutability is moot.  But changing
> them like
> adding/removing a layer does seem to work with the same pipeline.
>
> The following occurs ONLY on the first Actor I create with a new or
> copied
> pipeline.  All additional actors with a new or copied pipeline do not
> cause
> a leak.
>
> First case: I'm creating a pipeline, setting a texture on layer 0,
> drawing
> with it, then later unreffing the pipeline.  It seems that the
> pipeline
> would be freed but the texture did not because a pipeline layer held
> a
> reference to it.  I inserted a
> cogl_pipeline_set_layer_texture(pipeline, 0,
> NULL) in my code just before unreffing the pipeline and voila the
> texture
> was freed.
>
> In another version of the code I copy a pipeline, setting a texture
> on
> layer 0, drawing with it, then later unreffing the pipeline. It 
> seems
> again that the pipeline would be freed but the texture did not
> because a
> pipeline layer held a reference to it.  I inserted a
> cogl_pipeline_set_layer_texture(pipeline, 0, NULL) in my code just
> before
> unreffing the pipeline, but in this case the texture is not unreffed
> and
> freed.  In the routine _cogl_pipeline_set_layer_texture_data() for
> some
> reason for just the first actor and pipeline copy it takes the (new
> !=
> layer) condition and doesn't unref the texture which is done in the
> else
> clause (/* If the original layer we found is currently the authority
> on
> ...) for all subsequent actors / pipeline copies.
>
> Unfortunately if you have for the first actor and pipeline a
> 1024x1024
> texture and activate the atlas then you get a 2048x2048 atlas (16Mb
> of GPU
> RAM) that doesn't free up when the actor and pipeline copy is
> destroyed.
>
> Could anyone help me out here?
>
> Thanks,
>
> Reza
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