I have a graphics engine which for every frame writes approximately 300 bytes of data
with approximately six glTexSubImage2D calls to a texture (including writing to mipmaps).
The texture is a texture of unigned bytes using GL_RED and GL_R8 as format\internal format.
The uploading is performed via a pixel buffer, which in itself has been written to one frame ahead.
This quite small operation have a deep impact on the framerate regardless of what else gles is drawing.
Anyone have any idea of what is causing this frame rate drop, and how I can get past it?
Update: Solidpixels answer indicates it's a synchronization issue. In this case, I would be perfectly fine even if the texture modification is not synchronized at all with the rendering. Can I just tell gles to just write the data straight into the texture memory without caring at all if just half the new data is there?
Note:
It is only the glTexSubImage2D which affects the frame rate, the glSubBufferData upload does not affect at all.
On some devices it seems to mather when I actually perform the glTexSubImage2D in respect to when I draw using the texture, not all devices though.
I'd guess on the devices which slow down you still have outstanding references to the texture in flight, so you are forcing the drivers to create a ghost allocation. In depth explanation here: