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 492dc2b439a70f7a66dd6b2d0108bf753482c6ba..5103c98b694316fcf0537522316289aec8f263d3 100644
--- a/Source/platform/graphics/Canvas2DLayerBridge.cpp
+++ b/Source/platform/graphics/Canvas2DLayerBridge.cpp
@@ -41,6 +41,10 @@
 using blink::WebExternalTextureLayer;
 using blink::WebGraphicsContext3D;
 
+namespace {
+const size_t MaxSize = ~static_cast<size_t>(0);

[eseidel, 2013/12/19 02:56:32]

std::limits?

+}
+
 namespace WebCore {
 
 static PassRefPtr<SkSurface> createSkSurface(GraphicsContext3D* context3D, const IntSize& size, int msaaSampleCount)
@@ -58,7 +62,7 @@ static PassRefPtr<SkSurface> createSkSurface(GraphicsContext3D* context3D, const
     return adoptRef(SkSurface::NewRenderTarget(gr, info,  msaaSampleCount));
 }
 
-PassRefPtr<Canvas2DLayerBridge> Canvas2DLayerBridge::create(const IntSize& size, OpacityMode opacityMode, int msaaSampleCount)
+PassRefPtr<Canvas2DLayerBridge> Canvas2DLayerBridge::create(Canvas2DLayerBridgeClient* client, const IntSize& size, OpacityMode opacityMode, int msaaSampleCount)
 {
     TRACE_EVENT_INSTANT0("test_gpu", "Canvas2DLayerBridgeCreation");
     RefPtr<GraphicsContext3D> context = SharedGraphicsContext3D::get();
@@ -67,25 +71,29 @@ PassRefPtr<Canvas2DLayerBridge> Canvas2DLayerBridge::create(const IntSize& size,
         return 0;
     RefPtr<Canvas2DLayerBridge> layerBridge;
     OwnPtr<SkDeferredCanvas> canvas = adoptPtr(SkDeferredCanvas::Create(surface.get()));
-    layerBridge = adoptRef(new Canvas2DLayerBridge(context, canvas.release(), msaaSampleCount, opacityMode));
+    layerBridge = adoptRef(new Canvas2DLayerBridge(client, context, canvas.release(), msaaSampleCount, opacityMode));
     return layerBridge.release();
 }
 
-Canvas2DLayerBridge::Canvas2DLayerBridge(PassRefPtr<GraphicsContext3D> context, PassOwnPtr<SkDeferredCanvas> canvas, int msaaSampleCount, OpacityMode opacityMode)
-    : m_canvas(canvas)
+Canvas2DLayerBridge::Canvas2DLayerBridge(Canvas2DLayerBridgeClient* client, PassRefPtr<GraphicsContext3D> context, PassOwnPtr<SkDeferredCanvas> canvas, int msaaSampleCount, OpacityMode opacityMode)
+    : m_client(client)
+    , m_canvas(canvas)
     , m_context(context)
     , m_msaaSampleCount(msaaSampleCount)
     , m_bytesAllocated(0)
     , m_didRecordDrawCommand(false)
     , m_surfaceIsValid(true)
     , m_framesPending(0)
+    , m_framesSinceMailboxRelease(0)
     , m_destructionInProgress(false)
     , m_rateLimitingEnabled(false)
     , m_next(0)
     , m_prev(0)
     , m_lastImageId(0)
+    , m_releasedMailboxInfo(0)
 {
     ASSERT(m_canvas);
+    ASSERT(m_client);
     // Used by browser tests to detect the use of a Canvas2DLayerBridge.
     TRACE_EVENT_INSTANT0("test_gpu", "Canvas2DLayerBridgeCreation");
     m_layer = adoptPtr(blink::Platform::current()->compositorSupport()->createExternalTextureLayer(this));
@@ -100,18 +108,14 @@ 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();
 }
 
@@ -129,6 +133,23 @@ void Canvas2DLayerBridge::beginDestruction()
     m_layer->layer()->removeFromParent();
 }
 
+bool Canvas2DLayerBridge::hidden() const
+{
+    return m_destructionInProgress || m_client->hidden();
+}
+
+void Canvas2DLayerBridge::freeTransientResources()
+{
+    freeReleasedMailbox();
+    flush();
+    freeMemoryIfPossible(MaxSize);
+}
+
+bool Canvas2DLayerBridge::hasTransientResources() const
+{
+    return hasReleasedMailbox() || bytesAllocated();
+}
+
 void Canvas2DLayerBridge::limitPendingFrames()
 {
     ASSERT(!m_destructionInProgress);
@@ -144,6 +165,9 @@ void Canvas2DLayerBridge::limitPendingFrames()
             flush();
         }
     }
+    if (m_releasedMailboxInfo && ++m_framesSinceMailboxRelease >= 2) {
+        freeReleasedMailbox();
+    }
 }
 
 void Canvas2DLayerBridge::prepareForDraw()
@@ -214,10 +238,27 @@ void Canvas2DLayerBridge::flush()
     ASSERT(!m_destructionInProgress);
     if (m_canvas->hasPendingCommands()) {
         TRACE_EVENT0("cc", "Canvas2DLayerBridge::flush");
+        freeReleasedMailbox(); // To avoid unnecessary triple-buffering
         m_canvas->flush();
     }
 }
 
+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.
+        m_releasedMailboxInfo->m_image->getTexture()->invalidateCachedState();
+        m_releasedMailboxInfo->m_image.clear();
+        m_releasedMailboxInfo->m_status = MailboxAvailable;
+        m_releasedMailboxInfo = 0;
+    }
+}
+
 blink::WebGraphicsContext3D* Canvas2DLayerBridge::context()
 {
     // Check on m_layer is necessary because context() may be called during
@@ -277,28 +318,18 @@ bool Canvas2DLayerBridge::prepareMailbox(blink::WebExternalTextureMailbox* outMa
     // order to cap maximum gpu memory consumption.
     m_context->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) {
-                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();
-            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.
@@ -355,6 +386,7 @@ 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))) {
@@ -366,6 +398,13 @@ void Canvas2DLayerBridge::mailboxReleased(const blink::WebExternalTextureMailbox
             // referenced.
             ASSERT(mailboxInfo->m_parentLayerBridge.get() == this);
             mailboxInfo->m_parentLayerBridge.clear();
+            m_releasedMailboxInfo = mailboxInfo;
+            m_framesSinceMailboxRelease = 0;
+            if (hidden()) {
+                freeReleasedMailbox();
+            } else {
+                Canvas2DLayerManager::get().setLayerHasFreeableResources(this);
+            }
             return;
         }
     }
@@ -401,10 +440,10 @@ 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;
 }