Do not wait for rAF to be requested #114

Manishearth · 2019-12-19T19:56:16Z

This does not make the render loop completely independent of script: it still waits for script to submit a frame. If we don't, frames will be dropped (and I'm not sure what strategy to use there).

I'm going to test this soon and see if it actually improves our framerate.

Servo side: servo/servo#25343

r? @jdm


        Do not wait for rAF to be requested

Manishearth · 2019-12-19T19:56:57Z

webxr-api/session.rs

@@ -113,8 +113,8 @@ impl Session {
        let _ = self.sender.send(SessionMsg::SetSwapChain(swap_chain_id));
    }

-    pub fn request_animation_frame(&mut self, dest: Sender<Frame>) {
-        let _ = self.sender.send(SessionMsg::RequestAnimationFrame(dest));
+    pub fn start_render_loop(&mut self) {


This isn't strictly necessary, but makes things a bit easier

jdm · 2019-12-19T20:13:26Z

webxr-api/session.rs

+                        return false;
+                    }
+                };
+                let _ = self.frame_sender.send(frame);


So if I understand correctly, this is the big difference here - immediately after finishing a frame we wait for the new frame, but instead of storing it in current_frame and then grabbing it next time script tells us that it's time to start a rAF, we send it to script immediately which then causes a rAF callback task to be queued.

Yes. Note that in the current implementation script always calls request_animation_frame immediately after render_animation_frame, so it seems like this should not cause any improvement, however it's possible that the extra IPC overhead plus the fact that the event loop is being pumped by the main thread which may decide to do something else are conspiring to cause problems.

Manishearth · 2019-12-23T21:41:22Z

This provides a slight improvement, might as well land it. r? @jdm

jdm · 2019-12-24T00:42:40Z

@bors-servo r+

bors-servo · 2019-12-24T00:42:42Z

📌 Commit 58e8786 has been approved by jdm

bors-servo · 2019-12-24T00:42:45Z

⌛ Testing commit 58e8786 with merge c6abf4c...


        Auto merge of #114 - Manishearth:autoraf, r=jdm

@jdm

Do not wait for rAF to be requested This does not make the render loop _completely_ independent of script: it still waits for script to submit a frame. If we don't, frames will be dropped (and I'm not sure what strategy to use there). I'm going to test this soon and see if it actually improves our framerate. Servo side: servo/servo#25343 r? @jdm

bors-servo · 2019-12-24T00:49:30Z

☀️ Test successful - checks-travis
Approved by: jdm
Pushing c6abf4c to master...


        Auto merge of #25343 - Manishearth:autoraf, r=jdm

@jdm