From 564533ff295d200d3a5e265531f57a14b571fed1 Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Tue, 21 Apr 2020 09:57:47 -0700
Subject: [PATCH] Switch from Rust MPSC channels to `crossbeam-channel`.

7x performance improvement in contour.svg from MPVG!
---
 Cargo.lock                             | 1 +
 renderer/Cargo.toml                    | 1 +
 renderer/src/concurrent/scene_proxy.rs | 9 +++++----
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 257d0435..8e0f264d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1724,6 +1724,7 @@ version = "0.5.0"
 dependencies = [
  "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "byteorder 1.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "crossbeam-channel 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "half 1.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "hashbrown 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "instant 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/renderer/Cargo.toml b/renderer/Cargo.toml
index e8b5e180..da5e46b1 100644
--- a/renderer/Cargo.toml
+++ b/renderer/Cargo.toml
@@ -11,6 +11,7 @@ homepage = "https://github.com/servo/pathfinder"
 [dependencies]
 bitflags = "1.0"
 byteorder = "1.2"
+crossbeam-channel = "0.4"
 half = "1.5"
 hashbrown = "0.7"
 rayon = "1.0"
diff --git a/renderer/src/concurrent/scene_proxy.rs b/renderer/src/concurrent/scene_proxy.rs
index 861e7444..69cdf131 100644
--- a/renderer/src/concurrent/scene_proxy.rs
+++ b/renderer/src/concurrent/scene_proxy.rs
@@ -24,9 +24,9 @@ use crate::gpu::renderer::Renderer;
 use crate::gpu_data::RenderCommand;
 use crate::options::{BuildOptions, RenderCommandListener};
 use crate::scene::Scene;
+use crossbeam_channel::{self, Receiver, Sender};
 use pathfinder_geometry::rect::RectF;
 use pathfinder_gpu::Device;
-use std::sync::mpsc::{self, Receiver, Sender};
 use std::thread;
 
 const MAX_MESSAGES_IN_FLIGHT: usize = 1024;
@@ -42,7 +42,8 @@ impl SceneProxy {
 
     pub fn from_scene<E>(scene: Scene, executor: E) -> SceneProxy
                          where E: Executor + Send + 'static {
-        let (main_to_worker_sender, main_to_worker_receiver) = mpsc::channel();
+        let (main_to_worker_sender, main_to_worker_receiver) =
+            crossbeam_channel::bounded(MAX_MESSAGES_IN_FLIGHT);
         thread::spawn(move || scene_thread(scene, executor, main_to_worker_receiver));
         SceneProxy { sender: main_to_worker_sender }
     }
@@ -66,7 +67,7 @@ impl SceneProxy {
 
     #[inline]
     pub fn build_with_stream(&self, options: BuildOptions) -> RenderCommandStream {
-        let (sender, receiver) = mpsc::sync_channel(MAX_MESSAGES_IN_FLIGHT);
+        let (sender, receiver) = crossbeam_channel::bounded(MAX_MESSAGES_IN_FLIGHT);
         let listener = Box::new(move |command| drop(sender.send(command)));
         self.build_with_listener(options, listener);
         RenderCommandStream::new(receiver)
@@ -94,7 +95,7 @@ impl SceneProxy {
 
     #[inline]
     pub fn copy_scene(&self) -> Scene {
-        let (sender, receiver) = mpsc::channel();
+        let (sender, receiver) = crossbeam_channel::bounded(MAX_MESSAGES_IN_FLIGHT);
         self.sender.send(MainToWorkerMsg::CopyScene(sender)).unwrap();
         receiver.recv().unwrap()
     }