4 files changed, 60 insertions, 20 deletions

diff --git a/third_party/rust/wgpu-core/src/track/buffer.rs b/third_party/rust/wgpu-core/src/track/buffer.rs
index a30ac2a225..6cf1fdda6f 100644
--- a/third_party/rust/wgpu-core/src/track/buffer.rs
+++ b/third_party/rust/wgpu-core/src/track/buffer.rs
@@ -108,23 +108,27 @@ impl<A: HalApi> BufferBindGroupState<A> {
 #[derive(Debug)]
 pub(crate) struct BufferUsageScope<A: HalApi> {
     state: Vec<BufferUses>,
-
     metadata: ResourceMetadata<Buffer<A>>,
 }
 
-impl<A: HalApi> BufferUsageScope<A> {
-    pub fn new() -> Self {
+impl<A: HalApi> Default for BufferUsageScope<A> {
+    fn default() -> Self {
         Self {
             state: Vec::new(),
-
             metadata: ResourceMetadata::new(),
         }
     }
+}
 
+impl<A: HalApi> BufferUsageScope<A> {
     fn tracker_assert_in_bounds(&self, index: usize) {
         strict_assert!(index < self.state.len());
         self.metadata.tracker_assert_in_bounds(index);
     }
+    pub fn clear(&mut self) {
+        self.state.clear();
+        self.metadata.clear();
+    }
 
     /// Sets the size of all the vectors inside the tracker.
     ///
diff --git a/third_party/rust/wgpu-core/src/track/metadata.rs b/third_party/rust/wgpu-core/src/track/metadata.rs
index 744783a7fa..3e71e0e084 100644
--- a/third_party/rust/wgpu-core/src/track/metadata.rs
+++ b/third_party/rust/wgpu-core/src/track/metadata.rs
@@ -39,6 +39,11 @@ impl<T: Resource> ResourceMetadata<T> {
         resize_bitvec(&mut self.owned, size);
     }
 
+    pub(super) fn clear(&mut self) {
+        self.resources.clear();
+        self.owned.clear();
+    }
+
     /// Ensures a given index is in bounds for all arrays and does
     /// sanity checks of the presence of a refcount.
     ///
diff --git a/third_party/rust/wgpu-core/src/track/mod.rs b/third_party/rust/wgpu-core/src/track/mod.rs
index 9ca37ebadc..374dfe7493 100644
--- a/third_party/rust/wgpu-core/src/track/mod.rs
+++ b/third_party/rust/wgpu-core/src/track/mod.rs
@@ -480,8 +480,8 @@ impl<A: HalApi> RenderBundleScope<A> {
     /// Create the render bundle scope and pull the maximum IDs from the hubs.
     pub fn new() -> Self {
         Self {
-            buffers: RwLock::new(BufferUsageScope::new()),
-            textures: RwLock::new(TextureUsageScope::new()),
+            buffers: RwLock::new(BufferUsageScope::default()),
+            textures: RwLock::new(TextureUsageScope::default()),
             bind_groups: RwLock::new(StatelessTracker::new()),
             render_pipelines: RwLock::new(StatelessTracker::new()),
             query_sets: RwLock::new(StatelessTracker::new()),
@@ -512,28 +512,52 @@ impl<A: HalApi> RenderBundleScope<A> {
     }
 }
 
+/// A pool for storing the memory used by [`UsageScope`]s. We take and store this memory when the
+/// scope is dropped to avoid reallocating. The memory required only grows and allocation cost is
+/// significant when a large number of resources have been used.
+pub(crate) type UsageScopePool<A> = Mutex<Vec<(BufferUsageScope<A>, TextureUsageScope<A>)>>;
+
 /// A usage scope tracker. Only needs to store stateful resources as stateless
 /// resources cannot possibly have a usage conflict.
 #[derive(Debug)]
-pub(crate) struct UsageScope<A: HalApi> {
+pub(crate) struct UsageScope<'a, A: HalApi> {
+    pub pool: &'a UsageScopePool<A>,
     pub buffers: BufferUsageScope<A>,
     pub textures: TextureUsageScope<A>,
 }
 
-impl<A: HalApi> UsageScope<A> {
-    /// Create the render bundle scope and pull the maximum IDs from the hubs.
-    pub fn new(tracker_indices: &TrackerIndexAllocators) -> Self {
-        let mut value = Self {
-            buffers: BufferUsageScope::new(),
-            textures: TextureUsageScope::new(),
-        };
+impl<'a, A: HalApi> Drop for UsageScope<'a, A> {
+    fn drop(&mut self) {
+        // clear vecs and push into pool
+        self.buffers.clear();
+        self.textures.clear();
+        self.pool.lock().push((
+            std::mem::take(&mut self.buffers),
+            std::mem::take(&mut self.textures),
+        ));
+    }
+}
 
-        value.buffers.set_size(tracker_indices.buffers.size());
-        value.textures.set_size(tracker_indices.textures.size());
+impl<A: HalApi> UsageScope<'static, A> {
+    pub fn new_pooled<'d>(
+        pool: &'d UsageScopePool<A>,
+        tracker_indices: &TrackerIndexAllocators,
+    ) -> UsageScope<'d, A> {
+        let pooled = pool.lock().pop().unwrap_or_default();
+
+        let mut scope = UsageScope::<'d, A> {
+            pool,
+            buffers: pooled.0,
+            textures: pooled.1,
+        };
 
-        value
+        scope.buffers.set_size(tracker_indices.buffers.size());
+        scope.textures.set_size(tracker_indices.textures.size());
+        scope
     }
+}
 
+impl<'a, A: HalApi> UsageScope<'a, A> {
     /// Merge the inner contents of a bind group into the usage scope.
     ///
     /// Only stateful things are merged in here, all other resources are owned
diff --git a/third_party/rust/wgpu-core/src/track/texture.rs b/third_party/rust/wgpu-core/src/track/texture.rs
index e7c4707c93..3cf95ff38a 100644
--- a/third_party/rust/wgpu-core/src/track/texture.rs
+++ b/third_party/rust/wgpu-core/src/track/texture.rs
@@ -210,6 +210,7 @@ pub(crate) struct TextureStateSet {
     simple: Vec<TextureUses>,
     complex: FastHashMap<usize, ComplexTextureState>,
 }
+
 impl TextureStateSet {
     fn new() -> Self {
         Self {
@@ -235,15 +236,16 @@ pub(crate) struct TextureUsageScope<A: HalApi> {
     metadata: ResourceMetadata<Texture<A>>,
 }
 
-impl<A: HalApi> TextureUsageScope<A> {
-    pub fn new() -> Self {
+impl<A: HalApi> Default for TextureUsageScope<A> {
+    fn default() -> Self {
         Self {
             set: TextureStateSet::new(),
-
             metadata: ResourceMetadata::new(),
         }
     }
+}
 
+impl<A: HalApi> TextureUsageScope<A> {
     fn tracker_assert_in_bounds(&self, index: usize) {
         self.metadata.tracker_assert_in_bounds(index);
 
@@ -258,6 +260,11 @@ impl<A: HalApi> TextureUsageScope<A> {
         });
     }
 
+    pub fn clear(&mut self) {
+        self.set.clear();
+        self.metadata.clear();
+    }
+
     /// Sets the size of all the vectors inside the tracker.
     ///
     /// Must be called with the highest possible Texture ID before