Am 2017-01-17 um 22:55 schrieb Stefan Dösinger:
The one game that jumps out is Trackmania Nations. It apparently regressed from approx. 32 fps to 24. I will run a bisect in the next days to pinpoint the patch that caused this. The game itself wasn't updated.
I bisected this regression on the iMac itself, and the "bad" patch is 70889d68664c1211caf5a845014953dfee66c8f4. However, the patch is working as it is supposed to.
The game has a setting "GPU Synchro" that defaults to "Immediate". With this setting the game uses event queries to achieve the equivalent of glFinish(). Before 70889d68 an unsignalled event query would return S_OK and *data was set to FALSE. Now it returns S_FALSE and *data is left unset. This change in behavior makes the game's wait work as intended and the performance goes down.
Setting the synchronization to 1 frame (so the game waits for a query from one frame ago) restores the original performance.