One frame of rendering the "card" page in the gallery is using 4 fences. I suspect that is causing undo synchronizations between the gpu and cpu during a frame.

The first 2 fences are associated with getting notifications when resources can be cleaned up ( https://github.com/flutter/engine/blob/main/impeller/renderer/backend/vulkan/command_encoder_vk.cc#L173-L179 ). Synchronizing mid-frame to clean up resources is probably not what we want, but doing it once per frame is ideal.

I'm unsure what the last 2 fences are for. Are we submitting empty command buffers?

screenshot