Magma: wire-store rename spares 4 -> 12 with one fence question per rename, and a 50 us quiet window on unsignaled fence polls (FCL monolith GL CPU 2.44 -> 2.38 ms, 272 -> 278 fps at cpuhunt).

MobileGL/MG_Backend/DirectVulkan/Renderer/VkBufferManager.cpp

@@ -308,12 +308,13 @@ namespace MobileGL::MG_Backend::DirectVulkan {
             return false;
         VkBufferObject old = std::move(resource.buffer);
         Bool reused = false;
-        for (SizeT i = 0; pVulkanRenderer != nullptr && i < resource.renameSpares.size(); ++i) {
-            if (!pVulkanRenderer->IsSubmitIndexComplete(resource.renameSpares[i].submitIndex)) continue;
-            resource.buffer = std::move(resource.renameSpares[i].buffer);
-            resource.renameSpares.erase(resource.renameSpares.begin() + static_cast<std::ptrdiff_t>(i));
+        // Spares are queued in rename order, so their sync points only grow: when the oldest is not
+        // complete, no later one is (one fence question instead of one per spare).
+        if (pVulkanRenderer != nullptr && !resource.renameSpares.empty() &&
+            pVulkanRenderer->IsSubmitIndexComplete(resource.renameSpares.front().submitIndex)) {
+            resource.buffer = std::move(resource.renameSpares.front().buffer);
+            resource.renameSpares.erase(resource.renameSpares.begin());
             reused = true;
-            break;
         }
         if (!reused) {
             if (!CreateWireStoreBuffer(resource)) {
@@ -332,7 +333,11 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         // Busy means a GPU command recorded so far may name the old buffer: it waits behind this
         // frame's serial and the current sync point, whatever its own stamps said - as a spare
         // for the next rename, or (past the bound) through DeferWireRelease.
-        constexpr SizeT kRenameSpares = 4;
+        // P15: 4 spares recycled too few for frames in flight x renames per frame (FCL MC 1.21.5:
+        // VkBufferObject::Create 0.031 + the retired stores' Destroy 0.014 ms/frame). Only shadowed
+        // stores rename, and those are at most kWireShadowMaxStore (64 KiB), so 12 spares bound a
+        // resource's extra memory at 768 KiB.
+        constexpr SizeT kRenameSpares = 12;
         if (resource.renameSpares.size() >= kRenameSpares) {
             auto& oldest = resource.renameSpares.front();
             DeferWireRelease(std::move(oldest.buffer), oldest.lastUseSerial);

MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp

@@ -5837,8 +5837,24 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         if (submitIndex > m_submitCounter) {
             return false; // not even submitted; no point polling fences
         }
+        // P15: a fence just seen unsignaled is not polled again for a short while. Callers ask per
+        // buffer write (FCL MC 1.21.5: vkGetFenceStatus was 0.020 ms/frame), and every one of them
+        // treats "not yet" as "still busy" - rename, defer, report unsignaled - so a late "yes" costs
+        // at most kUnsignaledPollQuietNs of extra caution, never correctness.
+        constexpr Uint64 kUnsignaledPollQuietNs = 50000;
+        const Uint64 now = static_cast<Uint64>(std::chrono::duration_cast<std::chrono::nanoseconds>(
+            std::chrono::steady_clock::now().time_since_epoch()).count());
+        if (!m_inFlightSubmits.empty() && m_unsignaledPollFront == m_inFlightSubmits.front().submitIndex &&
+            now - m_unsignaledPollNs < kUnsignaledPollQuietNs) {
+            return false;
+        }
         RefreshCompletedSubmits();
-        return submitIndex <= m_completedSubmitCounter;
+        if (submitIndex <= m_completedSubmitCounter) return true;
+        if (!m_inFlightSubmits.empty()) {
+            m_unsignaledPollFront = m_inFlightSubmits.front().submitIndex;
+            m_unsignaledPollNs = now;
+        }
+        return false;
     }
 
     void VulkanRenderer::RegisterSubmit(VkFence fence, Bool pooledFence) {

MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.h

@@ -1018,6 +1018,9 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         Vector<VkFence> m_freeSubmitFences;
         Uint64 m_submitCounter = 0;
         Uint64 m_completedSubmitCounter = 0;
+        // IsSubmitIndexComplete's quiet window: the in-flight front last seen unsignaled, and when.
+        Uint64 m_unsignaledPollFront = 0;
+        Uint64 m_unsignaledPollNs = 0;
         // Drains since the last Present, gating the drain's frame-boundary-equivalent
         // work (arena rewind + cache aging): a presenting app's mid-frame
         // readbacks/waits must neither churn the transient caches nor accelerate the