I'd be curious to see message traces and UMAPC (user mode asynchronous procedure calls) traces of this between the two. My hypothesis is that Win10 does quite a

I'd be curious to see message traces and UMAPC (user mode asynchronous procedure calls) traces of this between the two. My hypothesis is that Win10 does quite a bit more in UMAPCs than win7 does in the interests of keeping the system 'responsive' even at the costs of latency. For those not aware UMAPCs only run when a thread is available in an 'alertable' state (see MSDN as that's not exactly simple to explain https://msdn.microsoft.com/en-us/library/windows/desktop/ms687069%28v=vs.85%29.aspx#alertablewaitfunctions https://msdn.microsoft.com/en-us/library/windows/desktop/ms6... ), as such they tend to wait for input or other runtime idle points unless the application makes very heavy use of windows built in asynchronous methods and alertable waits. I would also be curious to compare a D2D application versus a GDI application; as the majority of the work has gone to D2D in the last few years. Please note that D2D application in this case means one using a swap chain and device not an ID2DHWNDRenderTarget (this rasterizes and composites on the GPU but has GDI compatibility built in).