[Merged by Bors] - bevy_render: Batch insertion for prepare_uniform_components

[superdump]

Objective

• Make insertion of uniform components faster

Solution

• Use batch insertion in the prepare_uniform_components system
• Improves many_cubes -- sphere from ~42fps to ~43fps

[mockersf]

--- a/crates/bevy_render/src/render_component.rs
+++ b/crates/bevy_render/src/render_component.rs
@@ -107,22 +107,22 @@ fn prepare_uniform_components<C: Component>(
     render_queue: Res<RenderQueue>,
     mut component_uniforms: ResMut<ComponentUniforms<C>>,
     components: Query<(Entity, &C)>,
-    mut prev_len: Local<usize>,
 ) where
     C: AsStd140 + Clone,
 {
     component_uniforms.uniforms.clear();
-    let mut entities = Vec::with_capacity(*prev_len);
-    for (entity, component) in components.iter() {
-        entities.push((
-            entity,
-            (DynamicUniformIndex::<C> {
-                index: component_uniforms.uniforms.push(component.clone()),
-                marker: PhantomData,
-            },),
-        ));
-    }
-    *prev_len = entities.len();
+    let entities = components
+        .iter()
+        .map(|(entity, component)| {
+            (
+                entity,
+                (DynamicUniformIndex::<C> {
+                    index: component_uniforms.uniforms.push(component.clone()),
+                    marker: PhantomData,
+                },),
+            )
+        })
+        .collect::<Vec<_>>();
     commands.insert_or_spawn_batch(entities);

is even faster on my side
components is an exact sized iterator, I think std collect does smarter things with those than pushing individual values inside a vec

[superdump]

I didn't see any practical difference but I think it makes sense anyway.

[james7132]

Try using a Local<Vec<...>> here and clearing every frame instead of allocating a new Vec.

Alternatively, insert_or_spawn_batch takes an iterator. You could pass the iterator directly into it instead of collecting into a Vec here.

[cart]

This won't work. The iterator needs to be "owned" because the insertion is a deferred command. You can't "borrow" the Local vec.

[cart]

bors r+

[bors]

Pull request successfully merged into main.

Build succeeded:

• build-android
• build (nightly, ubuntu-latest)
• build (stable, macos-latest)
• build (stable, ubuntu-latest)
• build (stable, windows-latest)
• build-wasm (nightly, ubuntu-latest)
• build-wasm (stable, ubuntu-latest)
• check-benches
• check-doc
• check-markdown-links
• check-missing-examples-in-docs
• check-unused-dependencies
• ci
• markdownlint
• run-examples