Disabled preference for creating small buffers as committed when tight alignment is used

Author: adam-sawicki-a

include/D3D12MemAlloc.h

@@ -1051,6 +1051,11 @@ enum ALLOCATOR_FLAGS
     which may take longer than creating placed resources in existing heaps.
     Passing this flag will disable this committed preference globally for the allocator.
     It can also be disabled for a single allocation by using #ALLOCATION_FLAG_STRATEGY_MIN_TIME.
+
+    If the tight resource alignment feature is used by the library (which happens automatically whenever supported,
+    unless you use flag #ALLOCATOR_FLAG_DONT_USE_TIGHT_ALIGNMENT), then small buffers are not preferred as committed.
+    Long story short, you don't need to specify any of these flags.
+    The library chooses the most optimal method automatically.
     */
     ALLOCATOR_FLAG_DONT_PREFER_SMALL_BUFFERS_COMMITTED = 0x10,
     /** TODO document... */

src/D3D12MemAlloc.cpp

@@ -5999,7 +5999,7 @@ class AllocatorPimpl
     const bool m_UseMutex;
     const bool m_AlwaysCommitted;
     const bool m_MsaaAlwaysCommitted;
-    const bool m_PreferSmallBuffersCommitted;
+    bool m_PreferSmallBuffersCommitted;
     const bool m_UseTightAlignment;
     bool m_DefaultPoolsNotZeroed = false;
     ID3D12Device* m_Device; // AddRef
@@ -6192,6 +6192,14 @@ HRESULT AllocatorPimpl::Init(const ALLOCATOR_DESC& desc)
         if (SUCCEEDED(hr))
         {
             m_TightAlignmentSupported = tightAlignment.SupportTier >= D3D12_TIGHT_ALIGNMENT_TIER_1;
+            
+            // If tight alignment is supported (checked by the code above) and wasn't disabled by the developer
+            // (with ALLOCATOR_FLAG_DONT_USE_TIGHT_ALIGNMENT), disable the preference for creating small buffers as committed,
+            // as if ALLOCATOR_FLAG_DONT_PREFER_SMALL_BUFFERS_COMMITTED was specified.
+            if (IsTightAlignmentEnabled())
+            {
+                m_PreferSmallBuffersCommitted = false;
+            }
         }
     }
 #endif