Hello Everyone! I have a question about function glTexImage2D.
There is some code that cause GL memory leak on the devices with mali gpu (t760) and force close android application.
....
struct Vertex
{
float x, y, z;
float u, v;
};
...
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glViewport(0, 0, 1440, 2560);
while(true)
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texID);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 1440, 2560, 0, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
glUseProgram(shader);
int position = glGetAttribLocation(shader, "aPosition");
glVertexAttribPointer(hPosition, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), &vertexBuffer[0]);
glEnableVertexAttribArray(position);
int texCoord = glGetAttribLocation(data.shader, "aTexCoord");
glVertexAttribPointer(texCoord, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), &vertexBuffer[0].u);
glEnableVertexAttribArray(texCoord);
int textureLocation = glGetUniformLocation(shader, "texture0");
glUniform1i(textureLocation, 0);
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
glDisableVertexAttribArray(position);
glDisableVertexAttribArray(texCoord);
}
The shaders program is a trivial, just gets texture sampler and draws at the target FBO.
This code is just rendering texture into FBO. On each steps texture is updated by glTexImage2D call.
The question is why this code leads to memory leak?
I suppose, the reason is that glTexImage2D on each call allocates new chunk of memory for texture's data.
Texture memory that are used at previous rendering step is never released, until we call glFinish or glBindFramebuffer(GL_FRAMEBUFFER, 0).
It looks like some optimization on driver side, but is it standard behavior? Please, correct me if I'm wrong.
Thanks a lot!
P.S Code above works fine on the devices with Adreno GPU.
So, thanks guys for yours answers. It helps me understand how it works under hood.
All workaround was mentioned before (I think, the best one is periodically flush (for example, calls glFinish))
I believe, sometime we can see resolved this issue on the driver side
Kind regards,
Igor
Some general observations for "real app" behavior.
HTH, Pete