HnRenderParam: improved multithreaded performance of AddDirtyRPrim

DiligentGraphics · Jan 21, 2025 · f21f0a9 · f21f0a9
1 parent 60b4b21
commit f21f0a9
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Showing 2 changed files with 29 additions and 9 deletions.
diff --git a/Hydrogent/include/HnRenderParam.hpp b/Hydrogent/include/HnRenderParam.hpp
@@ -28,10 +28,12 @@
 
 #include <atomic>
 #include <array>
-#include <mutex>
 #include <vector>
+#include <unordered_map>
+#include <thread>
 
 #include "HnTypes.hpp"
+#include "SpinLock.hpp"
 
 #include "pxr/imaging/hd/renderDelegate.h"
 #include "../../PBR/interface/PBR_Renderer.hpp"
@@ -146,8 +148,11 @@ class HnRenderParam final : public pxr::HdRenderParam
     float    m_ElapsedTime = 0.0;
     uint32_t m_FrameNumber = 0;
 
-    std::mutex                                             m_DirtyRPrimsMtx;
-    std::vector<std::pair<pxr::SdfPath, pxr::HdDirtyBits>> m_DirtyRPrims;
+    using DirtyRPrimsVector = std::vector<std::pair<pxr::SdfPath, pxr::HdDirtyBits>>;
+
+    // Note: spin lock here works much faster than std::mutex
+    Threading::SpinLock                                    m_DirtyRPrimsLock;
+    std::unordered_map<std::thread::id, DirtyRPrimsVector> m_DirtyRPrimsPerThread;
 };
 
 } // namespace USD

diff --git a/Hydrogent/src/HnRenderParam.cpp b/Hydrogent/src/HnRenderParam.cpp
@@ -46,18 +46,33 @@ HnRenderParam::~HnRenderParam()
 
 void HnRenderParam::AddDirtyRPrim(const pxr::SdfPath& RPrimId, pxr::HdDirtyBits DirtyBits)
 {
-    std::lock_guard<std::mutex> Lock{m_DirtyRPrimsMtx};
-    m_DirtyRPrims.emplace_back(RPrimId, DirtyBits);
+    DirtyRPrimsVector* pDirtyRPrims = nullptr;
+    {
+        Threading::SpinLockGuard Guard{m_DirtyRPrimsLock};
+
+        auto it = m_DirtyRPrimsPerThread.find(std::this_thread::get_id());
+        if (it == m_DirtyRPrimsPerThread.end())
+        {
+            it = m_DirtyRPrimsPerThread.emplace(std::this_thread::get_id(), DirtyRPrimsVector{}).first;
+            it->second.reserve(16);
+        }
+        pDirtyRPrims = &it->second;
+    }
+    pDirtyRPrims->emplace_back(RPrimId, DirtyBits);
 }
 
 void HnRenderParam::CommitDirtyRPrims(pxr::HdChangeTracker& ChangeTracker)
 {
-    std::lock_guard<std::mutex> Lock{m_DirtyRPrimsMtx};
-    for (const auto& DidrtRPrim : m_DirtyRPrims)
+    Threading::SpinLockGuard Guard{m_DirtyRPrimsLock};
+
+    for (const auto& DirtyRPrims : m_DirtyRPrimsPerThread)
     {
-        ChangeTracker.MarkRprimDirty(DidrtRPrim.first, DidrtRPrim.second);
+        for (const auto& RPrim : DirtyRPrims.second)
+        {
+            ChangeTracker.MarkRprimDirty(RPrim.first, RPrim.second);
+        }
     }
-    m_DirtyRPrims.clear();
+    m_DirtyRPrimsPerThread.clear();
 }
 
 } // namespace USD