[snuxoll]

Every draw call will need to transition to kernel space to send data over the PCIe bus to the GPU. Modern games execute something on the order of 1000+ draws per frame, so assuming 60fps that's going to be at least 60,000*2 context switches into the kernel and back per second, more if you're doing high refresh rates.

How big the impact I will be, I don't know - but I wouldn't be surprised if it was a couple percent (effectively ruining the single-threaded performance boost Intel has in gaming over AMD before accounting for overclocking).

[TheSwordsman]

I was also worried about network I/O too, which could be an absolute pain for games where you care about latency.

[user5994461]

Network IO is negligible in game. The source engine for instance is hard limited to using 30 kB/s of bandwidth.