1612443 - Do frame building and rendering on the same thread

Status: NEW

(Core :: Graphics: WebRender, enhancement, P3)

Description

[Nicolas Silva [:nical]]

WebRender currently allows too much pipelining (see bug 1487864). Submitting draw calls on the same thread as frame building would have a number of benefits:

• remove some of this pipelining that is causing more harm than good,
• remove the latency between the time the renderer is notified and the time it wakes up (the event loop code isn't very efficient),
• allow us to submit drawing commands and uploads earlier in the frame.

To do this we need to be confident that frame-building and rendering are fast enough that the sum of the two always fits in the frame budget.

Instead of having a render backend thread, the render backend would move to the renderer thread (we currently have one render backend thread per window).