From aa4e2c56b561918aa51c66a86a3b54381bd2425e Mon Sep 17 00:00:00 2001
From: Doris Wu <doriswu@google.com>
Date: Sat, 15 Nov 2025 10:23:27 +0800
Subject: [PATCH] buffer update opt: Skip releaseFreeSlots when no frees are
 pending (#9437)

---
 filament/src/details/BufferAllocator.cpp | 17 +++++++++++++++--
 filament/src/details/BufferAllocator.h   |  3 ++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/filament/src/details/BufferAllocator.cpp b/filament/src/details/BufferAllocator.cpp
index 2e60dfdcc0..e7692b8ad0 100644
--- a/filament/src/details/BufferAllocator.cpp
+++ b/filament/src/details/BufferAllocator.cpp
@@ -142,7 +142,11 @@ void BufferAllocator::retire(AllocationId id) {
     InternalSlotNode* targetNode = getNodeById(id);
     assert_invariant(targetNode != nullptr);
 
-    targetNode->slot.isAllocated = false;
+    Slot& slot = targetNode->slot;
+    slot.isAllocated = false;
+    if (slot.gpuUseCount == 0) {
+        mHasPendingFrees = true;
+    }
 }
 
 void BufferAllocator::acquireGpu(AllocationId id) {
@@ -157,10 +161,18 @@ void BufferAllocator::releaseGpu(AllocationId id) {
     assert_invariant(targetNode != nullptr);
     assert_invariant(targetNode->slot.gpuUseCount > 0);
 
-    targetNode->slot.gpuUseCount--;
+    Slot& slot = targetNode->slot;
+    slot.gpuUseCount--;
+    if (slot.gpuUseCount == 0 && !slot.isAllocated) {
+        mHasPendingFrees = true;
+    }
 }
 
 void BufferAllocator::releaseFreeSlots() {
+    if (!mHasPendingFrees) {
+        return;
+    }
+
     auto curr = mSlotPool.begin();
     while (curr != mSlotPool.end()) {
         if (!curr->slot.isFree()) {
@@ -199,6 +211,7 @@ void BufferAllocator::releaseFreeSlots() {
 
         curr = next;
     }
+    mHasPendingFrees = false;
 }
 
 BufferAllocator::allocation_size_t BufferAllocator::getTotalSize() const noexcept {
diff --git a/filament/src/details/BufferAllocator.h b/filament/src/details/BufferAllocator.h
index f42c30588d..0cfdc568f9 100644
--- a/filament/src/details/BufferAllocator.h
+++ b/filament/src/details/BufferAllocator.h
@@ -113,8 +113,9 @@ private:
 
     [[nodiscard]] InternalSlotNode* getNodeById(AllocationId id) const noexcept;
 
+    bool mHasPendingFrees = false;
     allocation_size_t mTotalSize;
-    const allocation_size_t mSlotSize; // Size of a single slot in bytes.
+    const allocation_size_t mSlotSize; // Size of a single slot in bytes
     std::list<InternalSlotNode> mSlotPool; // All slots, including both allocated and freed
     std::multimap</*slot size*/allocation_size_t, InternalSlotNode*> mFreeList;
     std::unordered_map</*slot offset*/allocation_size_t, InternalSlotNode*> mOffsetMap;