source/blender/draw/engines/workbench/workbench_engine.cc

@@ -69,7 +69,7 @@ class Instance {
 
   void begin_sync()
   {
-    resources.material_buf.clear();
+    resources.material_buf.clear_and_trim();
 
     opaque_ps.sync(scene_state, resources);
     transparent_ps.sync(scene_state, resources);

source/blender/draw/intern/DRW_gpu_wrapper.hh

@@ -373,6 +373,20 @@ class StorageArrayBuffer : public detail::StorageCommon<T, len, device_only> {
     return this->data_[index];
   }
 
+  /*
+   * Ensure the allocated size is not much larger than the currently required size,
+   * using the same heuristic as `get_or_resize`.
+   */
+  void trim_to_next_power_of_2(int64_t required_size)
+  {
+    /* Don't go below the size used at creation. */
+    required_size = std::max(required_size, len);
+    size_t target_size = power_of_2_max_u(required_size);
+    if (this->len_ > target_size) {
+      this->resize(target_size);
+    }
+  }
+
   int64_t size() const
   {
     return this->len_;
@@ -414,6 +428,16 @@ class StorageVectorBuffer : public StorageArrayBuffer<T, len, false> {
     item_len_ = 0;
   }
 
+  /**
+   * Set item count to zero
+   * and trim the buffer if current size is much larger than the current item count.
+   */
+  void clear_and_trim()
+  {
+    this->trim_to_next_power_of_2(item_len_);
+    clear();
+  }
+
   /**
    * Insert a new element at the end of the vector.
    * This might cause a reallocation with the capacity is exceeded.

source/blender/draw/intern/draw_command.cc

@@ -701,7 +701,7 @@ void DrawMultiBuf::bind(RecordingState &state,
   prototype_buf_.push_update();
   /* Allocate enough for the expansion pass. */
   resource_id_buf_.get_or_resize(resource_id_count_ * (use_custom_ids ? 2 : 1));
-  /* Two command per group. */
+  /* Two commands per group (inverted and non-inverted scale). */
   command_buf_.get_or_resize(group_count_ * 2);
 
   if (prototype_count_ > 0) {

source/blender/draw/intern/draw_command.hh

@@ -443,7 +443,10 @@ class DrawCommandBuf {
   uint resource_id_count_ = 0;
 
  public:
-  void clear(){};
+  void clear()
+  {
+    resource_id_buf_.trim_to_next_power_of_2(resource_id_count_);
+  };
 
   void append_draw(Vector<Header, 0> &headers,
                    Vector<Undetermined, 0> &commands,
@@ -554,6 +557,11 @@ class DrawMultiBuf {
  public:
   void clear()
   {
+    group_buf_.trim_to_next_power_of_2(group_count_);
+    /* Two commands per group (inverted and non-inverted scale). */
+    command_buf_.trim_to_next_power_of_2(group_count_ * 2);
+    prototype_buf_.trim_to_next_power_of_2(prototype_count_);
+    resource_id_buf_.trim_to_next_power_of_2(resource_id_count_);
     header_id_counter_ = 0;
     group_count_ = 0;
     prototype_count_ = 0;

source/blender/draw/intern/draw_manager.cc

@@ -32,6 +32,11 @@ void Manager::begin_sync()
   bounds_buf.swap();
   infos_buf.swap();
 
+  matrix_buf.current().trim_to_next_power_of_2(resource_len_);
+  bounds_buf.current().trim_to_next_power_of_2(resource_len_);
+  infos_buf.current().trim_to_next_power_of_2(resource_len_);
+  attributes_buf.trim_to_next_power_of_2(attribute_len_);
+
   /* TODO: This means the reference is kept until further redraw or manager tear-down. Instead,
    * they should be released after each draw loop. But for now, mimics old DRW behavior. */
   for (GPUTexture *texture : acquired_textures) {