Free temporary GPU and memory resources held by inactive or hidden 2D canvases

Source/platform/graphics/Canvas2DLayerBridge.cpp

Index: Source/platform/graphics/Canvas2DLayerBridge.cpp
diff --git a/Source/platform/graphics/Canvas2DLayerBridge.cpp b/Source/platform/graphics/Canvas2DLayerBridge.cpp
index 7767b6b184ff7e3eb1814eb4cad69e56f45d5ce4..df8c062d4fbb06ace5847b25e93d9e8f1c1e5970 100644
--- a/Source/platform/graphics/Canvas2DLayerBridge.cpp
+++ b/Source/platform/graphics/Canvas2DLayerBridge.cpp
@@ -43,7 +43,7 @@ using blink::WebGraphicsContext3D;
 
 namespace WebCore {
 
-static PassRefPtr<SkSurface> createSkSurface(GraphicsContext3D* context3D, const IntSize& size, int msaaSampleCount)
+static PassRefPtr<SkSurface> createSkSurface(GraphicsContext3D* context3D, const IntSize& size, int msaaSampleCount = 0)
 {
     ASSERT(!context3D->webContext()->isContextLost());
     GrContext* gr = context3D->grContext();
@@ -79,11 +79,14 @@ Canvas2DLayerBridge::Canvas2DLayerBridge(PassRefPtr<GraphicsContext3D> context,
     , m_didRecordDrawCommand(false)
     , m_surfaceIsValid(true)
     , m_framesPending(0)
+    , m_framesSinceMailboxRelease(0)
     , m_destructionInProgress(false)
     , m_rateLimitingEnabled(false)
+    , m_isHidden(false)
     , m_next(0)
     , m_prev(0)
     , m_lastImageId(0)
+    , m_releasedMailboxInfo(0)
 {
     ASSERT(m_canvas);
     // Used by browser tests to detect the use of a Canvas2DLayerBridge.
@@ -100,18 +103,14 @@ Canvas2DLayerBridge::~Canvas2DLayerBridge()
 {
     ASSERT(m_destructionInProgress);
     m_layer.clear();
+    freeReleasedMailbox();
+#if !ASSERT_DISABLED
     Vector<MailboxInfo>::iterator mailboxInfo;
     for (mailboxInfo = m_mailboxes.begin(); mailboxInfo < m_mailboxes.end(); ++mailboxInfo) {
         ASSERT(mailboxInfo->m_status != MailboxInUse);
-        if (mailboxInfo->m_status == MailboxReleased) {
-            if (mailboxInfo->m_mailbox.syncPoint) {
-                context()->waitSyncPoint(mailboxInfo->m_mailbox.syncPoint);
-                mailboxInfo->m_mailbox.syncPoint = 0;
-            }
-            // Invalidate texture state in case the compositor altered it since the copy-on-write.
-            mailboxInfo->m_image->getTexture()->invalidateCachedState();
-        }
+        ASSERT(mailboxInfo->m_status != MailboxReleased);
     }
+#endif
     m_mailboxes.clear();
 }
 
@@ -119,19 +118,49 @@ void Canvas2DLayerBridge::beginDestruction()
 {
     ASSERT(!m_destructionInProgress);
     m_destructionInProgress = true;
+    freeTransientResources();
+    setIsHidden(true);
     GraphicsLayer::unregisterContentsLayer(m_layer->layer());
     m_canvas->setNotificationClient(0);
     m_layer->clearTexture();
-    Canvas2DLayerManager::get().layerToBeDestroyed(this);
     // Orphaning the layer is required to trigger the recration of a new layer
     // in the case where destruction is caused by a canvas resize. Test:
     // virtual/gpu/fast/canvas/canvas-resize-after-paint-without-layout.html
     m_layer->layer()->removeFromParent();
 }
 
+void Canvas2DLayerBridge::setIsHidden(bool hidden)
+{
+    bool newHiddenValue = hidden || m_destructionInProgress;
+    if (m_isHidden == newHiddenValue)
+        return;
+
+    m_isHidden = newHiddenValue;
+    if (isHidden()) {
+        freeTransientResources();
+    }
+}
+
+void Canvas2DLayerBridge::freeTransientResources()
+{
+    freeReleasedMailbox();
+    flush();
+    freeMemoryIfPossible(bytesAllocated());
+    ASSERT(!hasTransientResources());
+}
+
+bool Canvas2DLayerBridge::hasTransientResources() const
+{
+    return hasReleasedMailbox() || bytesAllocated();
+}
+
 void Canvas2DLayerBridge::limitPendingFrames()
 {
     ASSERT(!m_destructionInProgress);
+    if (isHidden()) {
+        freeTransientResources();
+        return;
+    }
     if (m_didRecordDrawCommand) {
         m_framesPending++;
         m_didRecordDrawCommand = false;
@@ -144,11 +173,14 @@ void Canvas2DLayerBridge::limitPendingFrames()
             flush();
         }
     }
+    ++m_framesSinceMailboxRelease;
+    if (releasedMailboxHasExpired()) {
+        freeReleasedMailbox();
+    }
 }
 
 void Canvas2DLayerBridge::prepareForDraw()
 {
-    ASSERT(!m_destructionInProgress);
     ASSERT(m_layer);
     if (!isValid()) {
         if (m_canvas) {
@@ -162,28 +194,24 @@ void Canvas2DLayerBridge::prepareForDraw()
 
 void Canvas2DLayerBridge::storageAllocatedForRecordingChanged(size_t bytesAllocated)
 {
-    ASSERT(!m_destructionInProgress);
     intptr_t delta = (intptr_t)bytesAllocated - (intptr_t)m_bytesAllocated;
     m_bytesAllocated = bytesAllocated;
-    Canvas2DLayerManager::get().layerAllocatedStorageChanged(this, delta);
+    Canvas2DLayerManager::get().layerTransientResourceAllocationChanged(this, delta);
 }
 
 size_t Canvas2DLayerBridge::storageAllocatedForRecording()
 {
-    ASSERT(!m_destructionInProgress);
     return m_canvas->storageAllocatedForRecording();
 }
 
 void Canvas2DLayerBridge::flushedDrawCommands()
 {
-    ASSERT(!m_destructionInProgress);
     storageAllocatedForRecordingChanged(storageAllocatedForRecording());
     m_framesPending = 0;
 }
 
 void Canvas2DLayerBridge::skippedPendingDrawCommands()
 {
-    ASSERT(!m_destructionInProgress);
     // Stop triggering the rate limiter if SkDeferredCanvas is detecting
     // and optimizing overdraw.
     setRateLimitingEnabled(false);
@@ -201,23 +229,51 @@ void Canvas2DLayerBridge::setRateLimitingEnabled(bool enabled)
 
 size_t Canvas2DLayerBridge::freeMemoryIfPossible(size_t bytesToFree)
 {
-    ASSERT(!m_destructionInProgress);
     size_t bytesFreed = m_canvas->freeMemoryIfPossible(bytesToFree);
-    if (bytesFreed)
-        Canvas2DLayerManager::get().layerAllocatedStorageChanged(this, -((intptr_t)bytesFreed));
     m_bytesAllocated -= bytesFreed;
+    if (bytesFreed)
+        Canvas2DLayerManager::get().layerTransientResourceAllocationChanged(this, -((intptr_t)bytesFreed));
     return bytesFreed;
 }
 
 void Canvas2DLayerBridge::flush()
 {
-    ASSERT(!m_destructionInProgress);
     if (m_canvas->hasPendingCommands()) {
         TRACE_EVENT0("cc", "Canvas2DLayerBridge::flush");
+        freeReleasedMailbox(); // To avoid unnecessary triple-buffering
         m_canvas->flush();
     }
 }
 
+bool Canvas2DLayerBridge::releasedMailboxHasExpired()
+{
+    // This heuristic indicates that the canvas is not being
+    // acitvely presented by the compositor, suggesting that it does

[Stephen White, 2014/01/27 18:55:14]

Nit: acitvely -> actively

Perhaps we should explain what the heuristic is; ie., the canvas hasn't been
drawn to in the last two frames (if that's what it is.)

+    // not require double buffering.
+    return m_releasedMailboxInfo && m_framesSinceMailboxRelease > 2;
+}
+
+void Canvas2DLayerBridge::freeReleasedMailbox()
+{
+    if (m_releasedMailboxInfo) {
+        ASSERT(m_releasedMailboxInfo->m_status == MailboxReleased);
+        if (m_releasedMailboxInfo->m_mailbox.syncPoint) {
+            context()->waitSyncPoint(m_releasedMailboxInfo->m_mailbox.syncPoint);
+            m_releasedMailboxInfo->m_mailbox.syncPoint = 0;
+        }
+        // Invalidate texture state in case the compositor altered it since the copy-on-write.
+        if (m_releasedMailboxInfo->m_image) {
+            if (isHidden() || releasedMailboxHasExpired())
+                m_releasedMailboxInfo->m_image->getTexture()->resetFlag(static_cast<GrTextureFlags>(GrTexture::kReturnToCache_FlagBit));
+            m_releasedMailboxInfo->m_image->getTexture()->invalidateCachedState();
+            m_releasedMailboxInfo->m_image.clear();
+        }
+        m_releasedMailboxInfo->m_status = MailboxAvailable;
+        m_releasedMailboxInfo = 0;
+        Canvas2DLayerManager::get().layerTransientResourceAllocationChanged(this);
+    }
+}
+
 blink::WebGraphicsContext3D* Canvas2DLayerBridge::context()
 {
     // Check on m_layer is necessary because context() may be called during
@@ -280,28 +336,18 @@ bool Canvas2DLayerBridge::prepareMailbox(blink::WebExternalTextureMailbox* outMa
     // order to cap maximum gpu memory consumption.
     webContext->makeContextCurrent();
     flush();
-    Vector<MailboxInfo>::iterator mailboxInfo;
-    for (mailboxInfo = m_mailboxes.begin(); mailboxInfo < m_mailboxes.end(); ++mailboxInfo) {
-        if (mailboxInfo->m_status == MailboxReleased) {
-            if (mailboxInfo->m_mailbox.syncPoint) {
-                webContext->waitSyncPoint(mailboxInfo->m_mailbox.syncPoint);
-                mailboxInfo->m_mailbox.syncPoint = 0;
-            }
-            // Invalidate texture state in case the compositor altered it since the copy-on-write.
-            mailboxInfo->m_image->getTexture()->invalidateCachedState();
-            mailboxInfo->m_image.reset(0);
-            mailboxInfo->m_status = MailboxAvailable;
-        }
-    }
-    SkAutoTUnref<SkImage> image(m_canvas->newImageSnapshot());
+
+    RefPtr<SkImage> image = adoptRef(m_canvas->newImageSnapshot());
+
     // Early exit if canvas was not drawn to since last prepareMailbox
     if (image->uniqueID() == m_lastImageId)
         return false;
     m_lastImageId = image->uniqueID();
 
-    mailboxInfo = createMailboxInfo();
+    MailboxInfo* mailboxInfo = createMailboxInfo();
     mailboxInfo->m_status = MailboxInUse;
-    mailboxInfo->m_image.swap(&image);
+    mailboxInfo->m_image = image;
+
     // Because of texture sharing with the compositor, we must invalidate
     // the state cached in skia so that the deferred copy on write
     // in SkSurface_Gpu does not make any false assumptions.
@@ -317,8 +363,14 @@ bool Canvas2DLayerBridge::prepareMailbox(blink::WebExternalTextureMailbox* outMa
     webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
     webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
     webContext->produceTextureCHROMIUM(GL_TEXTURE_2D, mailboxInfo->m_mailbox.name);
-    webContext->flush();
-    mailboxInfo->m_mailbox.syncPoint = webContext->insertSyncPoint();
+    if (isHidden()) {
+        // With hidden canvases, we release the SkImage immediately because
+        // there is no need for animations to be double buffered.
+        mailboxInfo->m_image.clear();
+    } else {
+        webContext->flush();
+        mailboxInfo->m_mailbox.syncPoint = webContext->insertSyncPoint();
+    }
     webContext->bindTexture(GL_TEXTURE_2D, 0);
     // Because we are changing the texture binding without going through skia,
     // we must dirty the context.
@@ -358,6 +410,7 @@ Canvas2DLayerBridge::MailboxInfo* Canvas2DLayerBridge::createMailboxInfo() {
 
 void Canvas2DLayerBridge::mailboxReleased(const blink::WebExternalTextureMailbox& mailbox)
 {
+    freeReleasedMailbox(); // Never have more than one mailbox in the released state.
     Vector<MailboxInfo>::iterator mailboxInfo;
     for (mailboxInfo = m_mailboxes.begin(); mailboxInfo < m_mailboxes.end(); ++mailboxInfo) {
         if (!memcmp(mailboxInfo->m_mailbox.name, mailbox.name, sizeof(mailbox.name))) {
@@ -367,6 +420,14 @@ void Canvas2DLayerBridge::mailboxReleased(const blink::WebExternalTextureMailbox
             // Trigger Canvas2DLayerBridge self-destruction if this is the
             // last live mailbox and the layer bridge is not externally
             // referenced.
+            m_releasedMailboxInfo = mailboxInfo;
+            m_framesSinceMailboxRelease = 0;
+            if (isHidden()) {
+                freeReleasedMailbox();
+            } else {
+                ASSERT(!m_destructionInProgress);
+                Canvas2DLayerManager::get().layerTransientResourceAllocationChanged(this);
+            }
             ASSERT(mailboxInfo->m_parentLayerBridge.get() == this);
             mailboxInfo->m_parentLayerBridge.clear();
             return;
@@ -404,10 +465,10 @@ Platform3DObject Canvas2DLayerBridge::getBackingTexture()
 
 Canvas2DLayerBridge::MailboxInfo::MailboxInfo(const MailboxInfo& other) {
     // This copy constructor should only be used for Vector reallocation
-    // Assuming 'other' is to be destroyed, we swap m_image ownership
+    // Assuming 'other' is to be destroyed, we transfer m_image ownership
     // rather than do a refcount dance.
     memcpy(&m_mailbox, &other.m_mailbox, sizeof(m_mailbox));
-    m_image.swap(const_cast<SkAutoTUnref<SkImage>*>(&other.m_image));
+    m_image = const_cast<MailboxInfo*>(&other)->m_image.release();
     m_status = other.m_status;
 }