For the last few weeks, I've been trying to port a DX9 implementation of HDR rendering (tone mapping, bloom, stars, etc.) over to DX11. I believe I've got all features working but I'm not getting good enough performance. I'd like to be able to render the whole effect in under 4ms on a fairly low-powered GPU, but using D3D11 Queries I'm noticing that it takes 0.5ms to just render a fullscreen quad with a solid color, and 1.0ms to render a fullscreen texture! And because tone-mapping is the only part of the effect that uses a fullscreen texture, this makes it the most expensive!
I'm already doing some optimisations with my limited graphics knowledge, I've disabled blending and depth-testing, I make sure that the texture sampler uses sensible filtering settings, and I'm pretty sure that the effects of any state-changes are negligible. I've heard that rendering 1 oversized triangle instead of 2 can yield some improvements, but I'm not sure if that will help me in this situation. Basically, does anyone have any suggestions to speed up rendering of a textured quad?