[Fix] (DirectVulkan): drain frame transients on present-less paths - readback waits, suspended presentation, blocking sync waits and flush completion polls now run Present's per-frame drains (deferred buffer/texture releases, transient arena rewind, descriptor cursors, retired command buffers, conversion caches) whenever every submission is provably complete, so offscreen/minimized workloads stay bounded; never blocks, frames-in-flight overlap untouched

MobileGL/MG_Backend/DirectVulkan/Renderer/FrameContext.cpp

@@ -264,7 +264,9 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         if (result != VK_SUCCESS) {
             return result;
         }
-        frame.retiredCommandBuffers.push_back(frame.commandBuffer);
+        // lastSubmitIndex was just written by the renderer for the submission
+        // that carried this command buffer.
+        frame.retiredCommandBuffers.push_back({frame.commandBuffer, frame.lastSubmitIndex});
         frame.commandBuffer = replacement;
         return VK_SUCCESS;
     }
@@ -274,12 +276,40 @@ namespace MobileGL::MG_Backend::DirectVulkan {
             return;
         }
         if (m_device != VK_NULL_HANDLE && m_commandPool != VK_NULL_HANDLE) {
-            vkFreeCommandBuffers(m_device, m_commandPool, static_cast<Uint32>(frame.retiredCommandBuffers.size()),
-                                 frame.retiredCommandBuffers.data());
+            for (const auto& retired : frame.retiredCommandBuffers) {
+                vkFreeCommandBuffers(m_device, m_commandPool, 1, &retired.commandBuffer);
+            }
         }
         frame.retiredCommandBuffers.clear();
     }
 
+    void FrameContext::FreeRetiredCommandBuffersCompletedUpTo(Uint64 completedSubmitIndex) {
+        if (m_device == VK_NULL_HANDLE || m_commandPool == VK_NULL_HANDLE) {
+            return;
+        }
+        for (auto& frame : m_frames) {
+            // Retired buffers are appended in submit order, so the completed
+            // ones form a prefix.
+            SizeT completedCount = 0;
+            while (completedCount < frame.retiredCommandBuffers.size() &&
+                   frame.retiredCommandBuffers[completedCount].submitIndex <= completedSubmitIndex) {
+                vkFreeCommandBuffers(m_device, m_commandPool, 1,
+                                     &frame.retiredCommandBuffers[completedCount].commandBuffer);
+                ++completedCount;
+            }
+            if (completedCount > 0) {
+                frame.retiredCommandBuffers.erase(frame.retiredCommandBuffers.begin(),
+                                                  frame.retiredCommandBuffers.begin() + completedCount);
+            }
+        }
+    }
+
+    void FrameContext::FreeAllRetiredCommandBuffers() {
+        for (auto& frame : m_frames) {
+            FreeRetiredCommandBuffers(frame);
+        }
+    }
+
     void FrameContext::AssertValidFrameIndex(Uint32 frameIndex) const {
         MOBILEGL_ASSERT(frameIndex < m_frames.size(), "FrameContext index out of range");
     }

MobileGL/MG_Backend/DirectVulkan/Renderer/FrameContext.h

@@ -40,6 +40,16 @@ namespace MobileGL::MG_Backend::DirectVulkan {
             VkPresentInfoKHR presentInfo{VK_STRUCTURE_TYPE_PRESENT_INFO_KHR};
         };
 
+        // A command buffer submitted mid-frame (FlushPendingCommands), tagged
+        // with the submit-tracker index it was submitted under so it can be
+        // freed as soon as that submission is observed complete - without
+        // waiting for the slot's fence to be waited again (present-less flush
+        // loops never wait it).
+        struct RetiredCommandBuffer {
+            VkCommandBuffer commandBuffer = VK_NULL_HANDLE;
+            Uint64 submitIndex = 0;
+        };
+
         struct FrameData {
             VkCommandBuffer commandBuffer = VK_NULL_HANDLE;
             VkSemaphore imageAvailableSemaphore = VK_NULL_HANDLE;
@@ -47,10 +57,10 @@ namespace MobileGL::MG_Backend::DirectVulkan {
             Bool isCommandRecording = false;
             Bool hasCommandBufferRecorded = false;
             Bool imageAvailableSemaphoreConsumed = false;
-            // Command buffers submitted mid-frame (FlushPendingCommands) whose
-            // execution is only known complete once this slot's fence has been
-            // waited again; freed at that point.
-            Vector<VkCommandBuffer> retiredCommandBuffers;
+            // Command buffers submitted mid-frame (FlushPendingCommands),
+            // appended in submit order; freed once their submission is known
+            // complete (fence wait or completion poll).
+            Vector<RetiredCommandBuffer> retiredCommandBuffers;
             // Submit-tracker index of this slot's most recent queue submission
             // (written by the renderer at submit time).
             Uint64 lastSubmitIndex = 0;
@@ -79,9 +89,19 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         // Parks the current (already ended and submitted) command buffer on the
         // slot's retired list and installs a freshly allocated one, so recording
         // can restart while the submitted buffer is still executing. Retired
-        // buffers are freed after the slot's fence is next waited.
+        // buffers are freed after the slot's fence is next waited, or as soon
+        // as their submission is observed complete.
         VkResult RetireCurrentCommandBuffer();
 
+        // Frees every retired command buffer whose tagged submission index is
+        // known complete. Driven by the renderer's submit tracker on completion
+        // events (fence waits and non-blocking polls), so present-less flush
+        // loops reclaim their buffers without any extra wait.
+        void FreeRetiredCommandBuffersCompletedUpTo(Uint64 completedSubmitIndex);
+        // Frees every slot's retired command buffers. Only valid when the
+        // caller has proven every queue submission complete.
+        void FreeAllRetiredCommandBuffers();
+
         Uint32 GetCurrentFrameIndex() const;
         Uint32 GetFrameCount() const;
 

MobileGL/MG_Backend/DirectVulkan/Renderer/VkBufferManager.cpp

@@ -141,6 +141,15 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         m_transientUploadArena.BeginFrame(frameIndex);
     }
 
+    void VkBufferManager::CollectAllDeferredReleases() {
+        for (Uint32 frameIndex = 0; frameIndex < m_deferredBufferReleases.size(); ++frameIndex) {
+            CollectDeferredReleases(frameIndex);
+        }
+        for (Uint32 frameIndex = 0; frameIndex < m_transientUploadArena.GetFrameCount(); ++frameIndex) {
+            m_transientUploadArena.CollectDeferredReleases(frameIndex);
+        }
+    }
+
     void VkBufferManager::NotifyDeviceIdle() {
         // Everything submitted so far has completed. Work recorded for the
         // current frame has not been submitted yet, so the current serial

MobileGL/MG_Backend/DirectVulkan/Renderer/VkBufferManager.h

@@ -77,6 +77,11 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         // Recreate all per-frame transient arenas
         Bool RecreateTransientArenas(Uint32 frameCount);
         void BeginFrame(Uint32 frameIndex);
+        // Drains every frame slot's deferred buffer/resource releases (and the
+        // transient arena's parked superseded blocks). Only valid when the
+        // caller has proven every queue submission complete; used by the
+        // present-less frame-boundary drain.
+        void CollectAllDeferredReleases();
         // All previously submitted GPU work has completed (vkDeviceWaitIdle).
         void NotifyDeviceIdle();
         // A frame slot's submission fence has been waited: every serial up to

MobileGL/MG_Backend/DirectVulkan/Renderer/VkTextureManager.cpp

@@ -629,6 +629,13 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         CollectDeferredReleases(frameIndex);
     }
 
+    void VkTextureManager::CollectAllDeferredReleases() {
+        const SizeT frameCount = std::min(m_deferredReleases.size(), m_deferredViewReleases.size());
+        for (SizeT frameIndex = 0; frameIndex < frameCount; ++frameIndex) {
+            CollectDeferredReleases(static_cast<Uint32>(frameIndex));
+        }
+    }
+
     void VkTextureManager::EraseTrackedTexture(const TextureIdentity& identity) {
         auto resourceIt = m_textureResources.find(identity);
         if (resourceIt != m_textureResources.end()) {

MobileGL/MG_Backend/DirectVulkan/Renderer/VkTextureManager.h

@@ -267,6 +267,10 @@ public:
     Bool Initialize(const InitInfo& initInfo);
     void Shutdown();
     void BeginFrame(Uint32 frameIndex);
+    // Drains every frame slot's deferred image/view releases. Only valid when
+    // the caller has proven every queue submission complete; used by the
+    // present-less frame-boundary drain.
+    void CollectAllDeferredReleases();
 
     TextureResource* SyncTextureAndGetDescriptor(
         MG_State::GLState::ITextureObject& texture);

MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp

@@ -6204,12 +6204,12 @@ void main() {
 
         frame.hasCommandBufferRecorded = false;
         frame.isCommandRecording = false;
-        // The wait proved every descriptor set this slot has in flight idle;
-        // rewind the reuse cursors so present-less readback loops stay
-        // bounded (Present is the only other rewind point).
-        if (m_uniformManager) {
-            m_uniformManager->BeginFrame(m_frameContext.GetCurrentFrameIndex());
-        }
+        // The wait proved every submission complete, so the full frame-boundary
+        // drain applies: descriptor cursors, transient arenas, deferred
+        // texture/buffer releases, retired command buffers and the converted
+        // vertex-stream cache all rewind here, keeping present-less readback
+        // loops bounded (Present is the only other drain point).
+        TryDrainFrameTransients();
         return true;
     }
 
@@ -7123,6 +7123,9 @@ void main() {
         }
         m_bufferManager.NotifyDeviceIdle();
         OnSubmitsCompletedUpTo(m_submitCounter);
+        // The queue was just drained; take the free frame-boundary drain when
+        // nothing is recorded (present-less timer-query loops). No-op otherwise.
+        TryDrainFrameTransients();
         return true;
     }
 
@@ -7191,6 +7194,54 @@ void main() {
                 vkDestroyFence(m_device, record.fence, nullptr);
             }
         }
+        // Mid-frame-flushed command buffers whose submission just completed can
+        // be freed now; present-less flush loops have no other reclaim point.
+        m_frameContext.FreeRetiredCommandBuffersCompletedUpTo(m_completedSubmitCounter);
+    }
+
+    Bool VulkanRenderer::TryDrainFrameTransients() {
+        if (m_device == VK_NULL_HANDLE || m_frameContext.GetFrameCount() == 0) {
+            return false;
+        }
+        if (m_completedSubmitCounter != m_submitCounter) {
+            RefreshCompletedSubmits();
+            if (m_completedSubmitCounter != m_submitCounter) {
+                return false;
+            }
+        }
+        if (HasPendingRecordedWork()) {
+            return false;
+        }
+
+        // Every submission is complete and nothing recorded references the
+        // per-frame transients, so the drains Present's tail performs are safe
+        // here too. Raise the buffer manager's completed floor first: the
+        // serial inference (frameSerial - frameCount) is only justified by
+        // Present's slot-fence cadence, and the extra BeginFrame below would
+        // otherwise inflate it past reality.
+        m_bufferManager.NotifyDeviceIdle();
+
+        const Uint32 frameIndex = m_frameContext.GetCurrentFrameIndex();
+        m_frameContext.FreeAllRetiredCommandBuffers();
+        for (Uint32 slot = 0; slot < m_deferredDepthMipmapCleanup.size(); ++slot) {
+            CollectDeferredDepthMipmapCleanup(slot);
+        }
+        if (m_textureManager) {
+            m_textureManager->CollectAllDeferredReleases();
+            m_textureManager->BeginFrame(frameIndex);
+        }
+        m_bufferManager.CollectAllDeferredReleases();
+        m_bufferManager.BeginFrame(frameIndex);
+        // The cached conversion slices point into the transient arena the
+        // BeginFrame above just rewound; drop them together.
+        m_convertedVertexStreams.clear();
+        if (m_uniformManager) {
+            m_uniformManager->BeginFrame(frameIndex);
+        }
+        if (m_renderPassManager) {
+            m_renderPassManager->OnPresent();
+        }
+        return true;
     }
 
     VkFence VulkanRenderer::AcquirePooledSubmitFence() {
@@ -7253,6 +7304,10 @@ void main() {
         if (m_device == VK_NULL_HANDLE || m_graphicsQueue == VK_NULL_HANDLE || m_frameContext.GetFrameCount() == 0) {
             return false;
         }
+        // Non-blocking completion poll: gives flush-only workloads (no sync
+        // objects, no present) a point where finished submissions retire their
+        // pooled fences and mid-frame command buffers.
+        RefreshCompletedSubmits();
         auto& frame = m_frameContext.GetCurrent();
         if (!frame.isCommandRecording && !frame.hasCommandBufferRecorded) {
             return false;
@@ -7328,6 +7383,10 @@ void main() {
                 const VkResult result = vkWaitForFences(m_device, 1, &record.fence, VK_TRUE, timeoutNs);
                 if (result == VK_SUCCESS) {
                     OnSubmitsCompletedUpTo(record.submitIndex);
+                    // The wait already stalled the pipeline; if it happens to
+                    // have drained everything (present-less fence loops), take
+                    // the free frame-boundary drain. No-op otherwise.
+                    TryDrainFrameTransients();
                     return true;
                 }
                 if (result != VK_TIMEOUT) {
@@ -7417,6 +7476,13 @@ void main() {
                 suspendedFrame.isCommandRecording = false;
                 suspendedFrame.hasCommandBufferRecorded = false;
                 m_lastPipelineValid = false;
+                // The dropped recording is never submitted, so once the fence
+                // poll shows the pre-suspension submissions complete the frame
+                // transients (descriptor sets, transient arenas, deferred
+                // releases, conversion caches) can rewind; without this a
+                // minimized-window app accumulates them for the whole
+                // suspension.
+                TryDrainFrameTransients();
                 MGLOG_D("Present skipped: no usable swapchain (zero-area window)");
                 return;
             }

MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.h

@@ -345,6 +345,15 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         VkFence AcquirePooledSubmitFence();
         void DestroySubmitFencePool();
         Bool HasPendingRecordedWork() const;
+        // Frame-boundary housekeeping for paths that never reach Present's
+        // tail (present-less readback loops, suspended presentation, blocking
+        // sync waits): runs the same per-frame drains Present performs, but
+        // only when every queue submission has been observed complete AND no
+        // recorded-but-unsubmitted commands exist - i.e. when CPU-GPU overlap
+        // is provably already zero. Never blocks (non-blocking fence poll
+        // only), so the presenting path's frames-in-flight pipelining is
+        // untouched. Returns true when the drain ran.
+        Bool TryDrainFrameTransients();
 
         Vector<SubmitRecord> m_inFlightSubmits;
         Vector<VkFence> m_freeSubmitFences;