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.
cgrant78 wrote: Looking at the ops code snippet I do not see anywhere where the allocated texture is deleted. The driver afaik is doing exactly what is asked of it..blindly allocating texture every iteration of the loop. If the texture is never deleted, how is the driver supposed to know that the texture will not be used in future ?
cgrant78 wrote:
Looking at the ops code snippet I do not see anywhere where the allocated texture is deleted. The driver afaik is doing exactly what is asked of it..blindly allocating texture every iteration of the loop. If the texture is never deleted, how is the driver supposed to know that the texture will not be used in future ?
The code only deals with a single texture handle, texID. Each iteration the texture is completely replaced and a single draw call performed referencing it, so from the API command stream we know that as soon as that draw is complete, we can discard that copy of the texture. There isn't an explicit flush in the command stream (glBindFramebuffer, eglSwapBuffers, glFinish etc) but after a while we should spot we have a large amount of data in flight and flush some of the command buffer to keep things reasonable, but that doesn't seem to be happening here.