From ecddb8aae5b211ce3a89da42e41e415887ae5ffc Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Sat, 7 Feb 2026 00:45:14 +0100
Subject: [PATCH] Optimize `GPUVertexLayout` caches with `ConcurrentDictionary`

---
 .../Graphics/Shaders/GPUVertexLayout.cpp      | 43 +++++++++----------
 1 file changed, 21 insertions(+), 22 deletions(-)

diff --git a/Source/Engine/Graphics/Shaders/GPUVertexLayout.cpp b/Source/Engine/Graphics/Shaders/GPUVertexLayout.cpp
index 6c34b2008..e458ff1c1 100644
--- a/Source/Engine/Graphics/Shaders/GPUVertexLayout.cpp
+++ b/Source/Engine/Graphics/Shaders/GPUVertexLayout.cpp
@@ -8,6 +8,7 @@
 #include "Engine/Graphics/GPUDevice.h"
 #include "Engine/Graphics/GPUBuffer.h"
 #include "Engine/Graphics/PixelFormatExtensions.h"
+#include "Engine/Threading/ConcurrentDictionary.h"
 #if GPU_ENABLE_RESOURCE_NAMING
 #include "Engine/Scripting/Enums.h"
 #endif
@@ -40,15 +41,12 @@ uint32 GetHash(const VertexBufferLayouts& key)
 
 namespace
 {
-    CriticalSection CacheLocker;
-    Dictionary<uint32, GPUVertexLayout*> LayoutCache;
-    Dictionary<VertexBufferLayouts, GPUVertexLayout*> VertexBufferCache;
+    ConcurrentDictionary<uint32, GPUVertexLayout*> LayoutCache;
+    ConcurrentDictionary<VertexBufferLayouts, GPUVertexLayout*> VertexBufferCache;
 
-    // TODO: it's not safe to use map and then use again with a lock (find a better way, eg. using two maps, one first read-only and thread safe, second with mutex-guarded new values from this frame)
-    GPUVertexLayout* AddCache(const VertexBufferLayouts& key, int32 count)
+    GPUVertexLayout* GetCache(const VertexBufferLayouts& key, int32 count)
     {
         GPUVertexLayout* result;
-        CacheLocker.Lock();
         if (!VertexBufferCache.TryGet(key, result))
         {
             GPUVertexLayout::Elements elements;
@@ -65,9 +63,15 @@ namespace
                 }
             }
             result = anyValid ? GPUVertexLayout::Get(elements, true) : nullptr;
-            VertexBufferCache.Add(key, result);
+            if (!VertexBufferCache.Add(key, result))
+            {
+                // Other thread added the value
+                Delete(result);
+                bool found = VertexBufferCache.TryGet(key, result);
+                ASSERT(found);
+            }
+
         }
-        CacheLocker.Unlock();
         return result;
     }
 }
@@ -155,7 +159,6 @@ GPUVertexLayout* GPUVertexLayout::Get(const Elements& elements, bool explicitOff
     }
 
     // Lookup existing cache
-    CacheLocker.Lock();
     GPUVertexLayout* result;
     if (!LayoutCache.TryGet(hash, result))
     {
@@ -167,12 +170,16 @@ GPUVertexLayout* GPUVertexLayout::Get(const Elements& elements, bool explicitOff
                 LOG(Error, " {}", e.ToString());
 #endif
             LOG(Error, "Failed to create vertex layout");
-            CacheLocker.Unlock();
             return nullptr;
         }
-        LayoutCache.Add(hash, result);
+        if (!LayoutCache.Add(hash, result))
+        {
+            // Other thread added the value
+            Delete(result);
+            bool found = LayoutCache.TryGet(hash, result);
+            ASSERT(found);
+        }
     }
-    CacheLocker.Unlock();
 
     return result;
 }
@@ -192,11 +199,7 @@ GPUVertexLayout* GPUVertexLayout::Get(const Span<GPUBuffer*>& vertexBuffers)
         key.Layouts[i] = nullptr;
 
     // Lookup existing cache
-    GPUVertexLayout* result;
-    if (!VertexBufferCache.TryGet(key, result))
-        result = AddCache(key, vertexBuffers.Length());
-
-    return result;
+    return GetCache(key, vertexBuffers.Length());
 }
 
 GPUVertexLayout* GPUVertexLayout::Get(const Span<GPUVertexLayout*>& layouts)
@@ -214,11 +217,7 @@ GPUVertexLayout* GPUVertexLayout::Get(const Span<GPUVertexLayout*>& layouts)
         key.Layouts[i] = nullptr;
 
     // Lookup existing cache
-    GPUVertexLayout* result;
-    if (!VertexBufferCache.TryGet(key, result))
-        result = AddCache(key, layouts.Length());
-
-    return result;
+    return GetCache(key, layouts.Length());
 }
 
 GPUVertexLayout* GPUVertexLayout::Merge(GPUVertexLayout* base, GPUVertexLayout* reference, bool removeUnused, bool addMissing, int32 missingSlotOverride, bool referenceOrder)