Legit Reviews posted a review on the Looking At DirectX 12 Performance ? 3DMark API Overhead Feature Test A quote from the article:

Gamers are more than excited about DirectX 12 coming to market later this year and after seeing what other low-level APIs like AMD Mantle could do with regards to lowering the API overhead we certainly understand why. Futuremark recently released a DirectX 12 feature test called the 3DMark API Overhead Feature Test that allows enthusiasts and gamers to look at the draw call benefits of the new DX12 API. The 3DMark API Overhead Feature Test should show how future game titles that were developed 'to the metal' perform.

 Looking At DirectX 12 Performance ? 3DMark API Overhead Feature Test @ Legit Reviews