Not really. OpenGL in particular has to do a surprising amount of work on every call, to make sure the state hasn't changed and to update all sorts of things if it has, to manage the various buffers and make sure they're mapped in the right place, and then to go down through all the abstraction layers until you end up in the code that actually writes stuff into the command buffer. It's not going to be a syscall level of overhead, though it may end up being that if stuff needs to get mapped into the GPU address space, but it's definitely going to be more than the dozen instruction overhead of going from JITed to native C++ code.