Sign in to follow this  

OpenGL Strange OpenGL Memory Leak

Recommended Posts

Hi everybody. I use OpenGL at work when working on the company's engine. Until now, everything was working in 2D ortho mode (using glVertex2f) and everything was fine. I recently needed to use 3D coordinates too (glVertex3f). I discovered a problem : I have a memory leak in the application (it uses ~70Mo of virtual memory and it slowly grows). If I use the engine more intensively, the groth speeds up : it can be as much as 1Mo each 5-10s !!! I traced everything in the code and it seems that, if I don't call glVertex3f/glVertex2f, then everything is just fine (but nothing is drawn on the screen). The solution to this memory leak is to call glClear (even with glClear(0)) each frame. Does anybody have any idea about this ? I run a Dell PIV 3Ghz with 1Go RAM and a NVidia Quadra with 512Mo with Windows XP. I tried two different drivers versions. The only people who seems to have the same problem has an ATI gfx card and no one answered his post, read it here). Thanks.

Share this post

Link to post
Share on other sites
Most programs typically do call glClear() once per frame, to at least clear the color buffer, so I guess it is remotely possible that the driver is using the glClear() call to free resources, but really that should happen on SwapBuffers() or at any rate on glFlush().

Try emailing NVidia about it, they should have a better idea than anyone why this happens.

Share this post

Link to post
Share on other sites
No, I tried it with a 50k polygon model, but didn't see any growth in the memory allocated to the application. I turned off depth testing and back face culling as well as not clearing the screen. I would say it is either specific to features you are using in the application or the driver for the card. If the program doesn't do it on an nVidia card then figure it is the driver. If it does the same thing there then figure it is some specific feature of the API you are using.

PS: Oops, thought you were running on a ATI card. I believe the Quadro drivers are differant than for the 6200 I'm using so while you are using a nVida driver already you might try it with a 6200, 6600, 6800 or 7800.

Share this post

Link to post
Share on other sites
Hi !

Thanks for your remarks and suggestions.

There is only a small chance that the memory leak comes from my code because two people (me included) checked it thouroughly and we didn't find anything. So, I guess I will have to write to NVidia. I think I will also try glIntercept too.

Anyway, thanks all.

Share this post

Link to post
Share on other sites
Guest Anonymous Poster
Try locating every 'new' (eg. char* test = new char) command. Sometimes every frame a 'new' is declared, so they pile up

Share this post

Link to post
Share on other sites
Guest Anonymous Poster
make sure you delete your textures after you use them and that your only loading the textures one time

other than that it sounds like a non opengl related problem, check all you mallocs for paired frees other than that the only way to know for sure is if you post your code

btw, my first opengl project had your symptoms, it was because i was loading textures everyframe - that would work if i paired every call to glgentextures with gldeletetexture, slowly, but no leaks

make sure you call gldeletetexture after your finished with a texture, or
gldeletelist after your done with a display list

you probably are calling glgen something every frame

hope that helps

Share this post

Link to post
Share on other sites
Hi everybody.

I indeed use multiple threads in the application but only one of them is using/calling OpenGL functions. The cause of the problem shouldn't come from multithreading.

A for new/delete pairs, every line of code regarding OpenGL has been examined and nothing was found. The previous version of the program hadn't the problem and I diff'ed the two sources and, again, no problematic code has been found.

I insist that the problem disappears as soon as I put a glClear() call on every frame (which shouldn't be needed as I'm rendering on the whole screen).

Anyway, thanks for your suggestions.

Share this post

Link to post
Share on other sites
I cannot reproduce this behaviour, neither on a GF4, 7800, Radeon X800, or Radeon Mobility 9700.

Of course a driver will allocate memory if you successively call IM commands without flushing the pipeline. They have to be cached somewhere, until they get pushed into the GPU command queue and processed. But this memory is either released, or recycled at some later point, not necessarily on swap buffers. Sometimes the grown queue can be kept at the new size, and will shrink at some later point because the driver expects the same large amount of data over the next frames. This avoids constant reallocation of memory at each frame.

Memory allocation policies are not specified by the standard, and are left at the discretion of the driver implementor. It is extremely unlikely that such a memory leak occurs on both an nvidia and ATI driver, at the exact same spot (unless NV or ATI have some serious case of corporate espionnage and source leaking going on ;). So there is a very large chance that your code is at fault.

Now, in a modern engine, it is pretty much expected that you call glClear each frame. It is not an optimization to avoid calling it, even if you draw over the entire frame ! In fact, not calling it can and will slow you down on modern GPUs. glClear does a lot more than simply clearing the framebuffers. It will also reset internal pixel occlusion and early z rejection structures, internal caches, can clear padded depth/stencil buffer very efficiently, etc. You should most definitely call it once per frame, even if just for performance reasons.

Now, if you are 100% positive that this memory leak is a driver issue, then try to write a short and basic code snippet that can reliably reproduce this behaviour. Post it here. If the effect can be reproduced by several people, then it is in fact a bug that can be submitted to NV or ATI. If not, it is probably your code.

Oh btw, there is a well known memory leak on ATI hardware if using several contexts. But this is not an issue on nvidia.

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Announcements

  • Forum Statistics

    • Total Topics
    • Total Posts
  • Similar Content

    • By test opty
      Hi all,
      I'm starting OpenGL using a tut on the Web. But at this point I would like to know the primitives needed for creating a window using OpenGL. So on Windows and using MS VS 2017, what is the simplest code required to render a window with the title of "First Rectangle", please?
    • By DejayHextrix
      Hi, New here. 
      I need some help. My fiance and I like to play this mobile game online that goes by real time. Her and I are always working but when we have free time we like to play this game. We don't always got time throughout the day to Queue Buildings, troops, Upgrades....etc.... 
      I was told to look into DLL Injection and OpenGL/DirectX Hooking. Is this true? Is this what I need to learn? 
      How do I read the Android files, or modify the files, or get the in-game tags/variables for the game I want? 
      Any assistance on this would be most appreciated. I been everywhere and seems no one knows or is to lazy to help me out. It would be nice to have assistance for once. I don't know what I need to learn. 
      So links of topics I need to learn within the comment section would be SOOOOO.....Helpful. Anything to just get me started. 
      Dejay Hextrix 
    • By mellinoe
      Hi all,
      First time poster here, although I've been reading posts here for quite a while. This place has been invaluable for learning graphics programming -- thanks for a great resource!
      Right now, I'm working on a graphics abstraction layer for .NET which supports D3D11, Vulkan, and OpenGL at the moment. I have implemented most of my planned features already, and things are working well. Some remaining features that I am planning are Compute Shaders, and some flavor of read-write shader resources. At the moment, my shaders can just get simple read-only access to a uniform (or constant) buffer, a texture, or a sampler. Unfortunately, I'm having a tough time grasping the distinctions between all of the different kinds of read-write resources that are available. In D3D alone, there seem to be 5 or 6 different kinds of resources with similar but different characteristics. On top of that, I get the impression that some of them are more or less "obsoleted" by the newer kinds, and don't have much of a place in modern code. There seem to be a few pivots:
      The data source/destination (buffer or texture) Read-write or read-only Structured or unstructured (?) Ordered vs unordered (?) These are just my observations based on a lot of MSDN and OpenGL doc reading. For my library, I'm not interested in exposing every possibility to the user -- just trying to find a good "middle-ground" that can be represented cleanly across API's which is good enough for common scenarios.
      Can anyone give a sort of "overview" of the different options, and perhaps compare/contrast the concepts between Direct3D, OpenGL, and Vulkan? I'd also be very interested in hearing how other folks have abstracted these concepts in their libraries.
    • By aejt
      I recently started getting into graphics programming (2nd try, first try was many years ago) and I'm working on a 3d rendering engine which I hope to be able to make a 3D game with sooner or later. I have plenty of C++ experience, but not a lot when it comes to graphics, and while it's definitely going much better this time, I'm having trouble figuring out how assets are usually handled by engines.
      I'm not having trouble with handling the GPU resources, but more so with how the resources should be defined and used in the system (materials, models, etc).
      This is my plan now, I've implemented most of it except for the XML parts and factories and those are the ones I'm not sure of at all:
      I have these classes:
      For GPU resources:
      Geometry: holds and manages everything needed to render a geometry: VAO, VBO, EBO. Texture: holds and manages a texture which is loaded into the GPU. Shader: holds and manages a shader which is loaded into the GPU. For assets relying on GPU resources:
      Material: holds a shader resource, multiple texture resources, as well as uniform settings. Mesh: holds a geometry and a material. Model: holds multiple meshes, possibly in a tree structure to more easily support skinning later on? For handling GPU resources:
      ResourceCache<T>: T can be any resource loaded into the GPU. It owns these resources and only hands out handles to them on request (currently string identifiers are used when requesting handles, but all resources are stored in a vector and each handle only contains resource's index in that vector) Resource<T>: The handles given out from ResourceCache. The handles are reference counted and to get the underlying resource you simply deference like with pointers (*handle).  
      And my plan is to define everything into these XML documents to abstract away files:
      Resources.xml for ref-counted GPU resources (geometry, shaders, textures) Resources are assigned names/ids and resource files, and possibly some attributes (what vertex attributes does this geometry have? what vertex attributes does this shader expect? what uniforms does this shader use? and so on) Are reference counted using ResourceCache<T> Assets.xml for assets using the GPU resources (materials, meshes, models) Assets are not reference counted, but they hold handles to ref-counted resources. References the resources defined in Resources.xml by names/ids. The XMLs are loaded into some structure in memory which is then used for loading the resources/assets using factory classes:
      Factory classes for resources:
      For example, a texture factory could contain the texture definitions from the XML containing data about textures in the game, as well as a cache containing all loaded textures. This means it has mappings from each name/id to a file and when asked to load a texture with a name/id, it can look up its path and use a "BinaryLoader" to either load the file and create the resource directly, or asynchronously load the file's data into a queue which then can be read from later to create the resources synchronously in the GL context. These factories only return handles.
      Factory classes for assets:
      Much like for resources, these classes contain the definitions for the assets they can load. For example, with the definition the MaterialFactory will know which shader, textures and possibly uniform a certain material has, and with the help of TextureFactory and ShaderFactory, it can retrieve handles to the resources it needs (Shader + Textures), setup itself from XML data (uniform values), and return a created instance of requested material. These factories return actual instances, not handles (but the instances contain handles).
      Is this a good or commonly used approach? Is this going to bite me in the ass later on? Are there other more preferable approaches? Is this outside of the scope of a 3d renderer and should be on the engine side? I'd love to receive and kind of advice or suggestions!
    • By nedondev
      I 'm learning how to create game by using opengl with c/c++ coding, so here is my fist game. In video description also have game contain in Dropbox. May be I will make it better in future.
  • Popular Now