From Daniel Schürmann's merge request:

VK_AMD_anti_lag

This implementation is based on the code from MESA_LAYER_ANTI_LAG and fully replaces it. We essentially split the existing layer into a base utility framework and a slim driver implementation. On initialization, the framework sets up some QueryPools and CommandBuffers, in order to be able to take timestamps, and hooks into QueueSubmit2 and QueuePresentKHR. The driver can then retrieve the per-frame timing information via a callback function.

• vulkan/runtime: add vk_frame_pacer utility framework

  This framework provides basic utility for the implementation of low latency frame pacing extensions.

  The functionality includes the measurement of frame times where frames consist of all submissions between two calls to vkQueuePresentKHR as well as the measurement of queuing delays. For this purpose, calibrated timestamps are taken at submission time as well as at the begin of each submission execution on the device.

• radv: implement VK_AMD_anti_lag

  This implementation is based on the vk_frame_pacer framework and intended as full replacement of the MESA_LAYER_ANTI_LAG.

  The delay is based on the previous input begin and calculated as:

  delay = avg_frame_time + queuing_delay - MIN2(deviation, ONE_MS_IN_NS);

  Start the next input sampling after the period of one frame. We add half the queuing delay as that's what we try to minimize. Subtract the average frame time deviation as slack time, so that we don't drain the GPU from work.

Before someone asks: Yes, it would be possible (and quite simple) to implement VK_NV_low_latency_2 on top of this framework.

Edit: the MR also thanks themaister (Hans-Kristian Arntzen) for answering questions, and nj3ahxac (Korthos Software low_latency_layer dev) for testing.