[kuschku]

That's why I said in absolute worst case scenario. I know that in the past I actually wrote some program in high school that did use that.

Nowadays, thanks to vulkan and AZDO with glMultiDrawElementsIndirect, you're right, of course — you might even use a single syscall per frame.

That's why I said, in absolute worst case.

[badsectoracula]

No i meant explicitly about the part i quoted: the immediate mode. Stuff like glBegin, glVertex3f, glEnd, etc. Those will not get you a syscall per vertex, they will be buffered by the OpenGL implementation. Modern OpenGL implementations, at least those by Nvidia and AMD (and i also suspect Mesa too) do a lot of optimizations on the client side.