Few Queries regarding rendering time calculation

[spaul13]

First of all, thanks for this great project. I want to know if we consider GL_EXT_disjoint_timer_query, what additional influence it has.

What I have seen glBeginQuery and glEndQuery blocking commands. You used those to get the rendering time whereas using GL_EXT_disjoint_timer_query we can get the time without stalling the rendering pipeline. Is that means here we can have measured rendering time >= actual rendering time?
If you have any idea how to use GL_EXT_disjoint_timer_query, please tell me.

One another question, this time is obtained from the GPU timer (not same as CPU time). Is there any way to get the CPU time elapsed during rendering?
Just want to know is there any way to include the time taken for CPU to send draw calls to GPU before the glBeginQuery()?

Why you choose initial buffer-size to be 4?

From my understanding, you are calculating the time taken by each query object if the buffer is non-empty. But while rendering each frame, we can have numerous query objects (draw calls). Just to clarify, are you taking the cumulative elapsed time until the command buffer size is zero?

Again this project is really very helpful.