When going back to a simple page like the attached testcase, the compositing layer is created without accelerated drawing enabled and never updated thereafter.
Created attachment 324716 [details] Testcase
<rdar://problem/35158946>
There are two things going on here. First, in GraphicsLayerCA::commitLayerChangesBeforeSublayers() we call updateTiles() before updateAcceleratesDrawing(), so it's possible for tiles to not get accelerated. Second, we create GraphicsLayers under style resolution, which happens before RenderLayerCompositor::cacheAcceleratedCompositingFlags(), so m_acceleratedDrawingEnabled is still false there.
Backtrace for creating compositing layers under style change: * frame #0: 0x00000007ea56b01a WebCore`WebCore::RenderLayerBacking::createPrimaryGraphicsLayer(this=0x00000007fb9fb630) at RenderLayerBacking.cpp:391 frame #1: 0x00000007ea56ae54 WebCore`WebCore::RenderLayerBacking::RenderLayerBacking(this=0x00000007fb9fb630, layer=0x00000007fb9975c8) at RenderLayerBacking.cpp:216 frame #2: 0x00000007ea56b9dd WebCore`WebCore::RenderLayerBacking::RenderLayerBacking(this=0x00000007fb9fb630, layer=0x00000007fb9975c8) at RenderLayerBacking.cpp:210 frame #3: 0x00000007ea5557db WebCore`WebCore::RenderLayer::ensureBacking() [inlined] std::__1::__unique_if<WebCore::RenderLayerBacking>::__unique_single std::__1::make_unique<WebCore::RenderLayerBacking, WebCore::RenderLayer&>(__args=0x00000007fb9975c8) at memory:3006 frame #4: 0x00000007ea5557b2 WebCore`WebCore::RenderLayer::ensureBacking(this=0x00000007fb9975c8) at RenderLayer.cpp:5911 frame #5: 0x00000007ea5936d8 WebCore`WebCore::RenderLayerCompositor::updateBacking(this=0x00000007fb9b1b10, layer=0x00000007fb9975c8, shouldRepaint=CompositingChangeRepaintNow, backingRequired=Yes) at RenderLayerCompositor.cpp:1020 frame #6: 0x00000007ea592f38 WebCore`WebCore::RenderLayerCompositor::updateLayerCompositingState(this=0x00000007fb9b1b10, layer=0x00000007fb9975c8, shouldRepaint=CompositingChangeRepaintNow) at RenderLayerCompositor.cpp:1109 frame #7: 0x00000007ea592e42 WebCore`WebCore::RenderLayerCompositor::layerStyleChanged(this=0x00000007fb9b1b10, diff=StyleDifferenceNewStyle, layer=0x00000007fb9975c8, oldStyle=0x0000000000000000) at RenderLayerCompositor.cpp:933 frame #8: 0x00000007ea55904d WebCore`WebCore::RenderLayer::styleChanged(this=0x00000007fb9975c8, diff=StyleDifferenceNewStyle, oldStyle=0x0000000000000000) at RenderLayer.cpp:6635 frame #9: 0x00000007ea5aeec6 WebCore`WebCore::RenderLayerModelObject::styleDidChange(this=0x00000007fe4786c0, diff=StyleDifferenceNewStyle, oldStyle=0x0000000000000000) at RenderLayerModelObject.cpp:193 frame #10: 0x00000007ea45ac22 WebCore`WebCore::RenderBox::styleDidChange(this=0x00000007fe4786c0, diff=StyleDifferenceNewStyle, oldStyle=0x0000000000000000) at RenderBox.cpp:302 frame #11: 0x00000007ea3d3602 WebCore`WebCore::RenderBlock::styleDidChange(this=0x00000007fe4786c0, diff=StyleDifferenceNewStyle, oldStyle=0x0000000000000000) at RenderBlock.cpp:432 frame #12: 0x00000007ea4245c3 WebCore`WebCore::RenderBlockFlow::styleDidChange(this=0x00000007fe4786c0, diff=StyleDifferenceNewStyle, oldStyle=0x0000000000000000) at RenderBlockFlow.cpp:2011 frame #13: 0x00000007ea4bed34 WebCore`WebCore::RenderElement::initializeStyle(this=0x00000007fe4786c0) at RenderElement.cpp:380 frame #14: 0x00000007ea73ea0c WebCore`WebCore::RenderTreeUpdater::createRenderer(this=0x00007ffee2db2360, element=0x00000007fe44d0d0, style=0x00007ffee2daf5d0) at RenderTreeUpdater.cpp:373 frame #15: 0x00000007ea73df18 WebCore`WebCore::RenderTreeUpdater::updateElementRenderer(this=0x00007ffee2db2360, element=0x00000007fe44d0d0, update=0x00000007fbbda950) at RenderTreeUpdater.cpp:326 frame #16: 0x00000007ea73d611 WebCore`WebCore::RenderTreeUpdater::updateRenderTree(this=0x00007ffee2db2360, root=0x00000007fb956000) at RenderTreeUpdater.cpp:198 frame #17: 0x00000007ea73cf59 WebCore`WebCore::RenderTreeUpdater::commit(this=0x00007ffee2db2360, styleUpdate=unique_ptr<const WebCore::Style::Update, std::__1::default_delete<const WebCore::Style::Update> > @ 0x00007ffee2db2358) at RenderTreeUpdater.cpp:134 frame #18: 0x00000007e87a7632 WebCore`WebCore::Document::resolveStyle(this=0x00000007fb956000, type=Rebuild) at Document.cpp:1825 frame #19: 0x00000007e87ab1be WebCore`WebCore::Document::createRenderTree(this=0x00000007fb956000) at Document.cpp:2172 frame #20: 0x00000007e87ab375 WebCore`WebCore::Document::didBecomeCurrentDocumentInFrame(this=0x00000007fb956000) at Document.cpp:2183
Created attachment 324770 [details] Patch
Created attachment 324772 [details] Patch
Comment on attachment 324772 [details] Patch Attachment 324772 [details] did not pass mac-ews (mac): Output: http://webkit-queues.webkit.org/results/4978945 New failing tests: compositing/iframes/page-cache-layer-tree.html
Created attachment 324781 [details] Archive of layout-test-results from ews102 for mac-elcapitan The attached test failures were seen while running run-webkit-tests on the mac-ews. Bot: ews102 Port: mac-elcapitan Platform: Mac OS X 10.11.6
Comment on attachment 324772 [details] Patch Attachment 324772 [details] did not pass mac-debug-ews (mac): Output: http://webkit-queues.webkit.org/results/4978912 New failing tests: compositing/iframes/page-cache-layer-tree.html
Created attachment 324782 [details] Archive of layout-test-results from ews114 for mac-elcapitan The attached test failures were seen while running run-webkit-tests on the mac-debug-ews. Bot: ews114 Port: mac-elcapitan Platform: Mac OS X 10.11.6
Comment on attachment 324772 [details] Patch Attachment 324772 [details] did not pass ios-sim-ews (ios-simulator-wk2): Output: http://webkit-queues.webkit.org/results/4978954 New failing tests: compositing/accelerated-layers-after-back.html compositing/iframes/page-cache-layer-tree.html
Created attachment 324785 [details] Archive of layout-test-results from ews121 for ios-simulator-wk2 The attached test failures were seen while running run-webkit-tests on the ios-sim-ews. Bot: ews121 Port: ios-simulator-wk2 Platform: Mac OS X 10.12.6
Comment on attachment 324772 [details] Patch Attachment 324772 [details] did not pass mac-wk2-ews (mac-wk2): Output: http://webkit-queues.webkit.org/results/4979670 New failing tests: compositing/iframes/page-cache-layer-tree.html
Created attachment 324794 [details] Archive of layout-test-results from ews105 for mac-elcapitan-wk2 The attached test failures were seen while running run-webkit-tests on the mac-wk2-ews. Bot: ews105 Port: mac-elcapitan-wk2 Platform: Mac OS X 10.11.6
https://trac.webkit.org/r223984
This change caused LayoutTests to hit an assertion failure: ASSERTION FAILED: !m_renderView.needsLayout() /Volumes/Data/slave/ios-simulator-11-debug/build/Source/WebCore/rendering/RenderLayerCompositor.cpp(2356) : bool WebCore::RenderLayerCompositor::requiresCompositingForScrollableFrame() const 1 0x1169bd9dd WTFCrash 2 0x11b86be5a WebCore::RenderLayerCompositor::requiresCompositingForScrollableFrame() const 3 0x11b86ba40 WebCore::RenderLayerCompositor::cacheAcceleratedCompositingFlags() 4 0x11b86bed9 WebCore::RenderLayerCompositor::willRecalcStyle() 5 0x11b13b95a WebCore::FrameView::willRecalcStyle() 6 0x11a941585 WebCore::Document::resolveStyle(WebCore::Document::ResolveStyleType) 7 0x11a9431f4 WebCore::Document::updateStyleIfNeeded() 8 0x11b13f1b5 WebCore::FrameView::updateStyleForLayout() 9 0x11b13d80e WebCore::FrameView::layout() 10 0x11b964b95 WebCore::RenderWidget::updateWidgetPosition() 11 0x11b14083a WebCore::FrameView::updateWidgetPositions() 12 0x11b13818f WebCore::FrameView::performPostLayoutTasks() 13 0x11b140651 WebCore::FrameView::runOrSchedulePostLayoutTasks() 14 0x11b13e1b5 WebCore::FrameView::layout() 15 0x11b150114 WebCore::FrameView::updateLayoutAndStyleIfNeededRecursive() 16 0x10daf8ff5 WebKit::WebPage::layoutIfNeeded() 17 0x10d72871e WebKit::RemoteLayerTreeDrawingArea::flushLayers() 18 0x10d72ff21 WTF::Function<void ()>::CallableWrapper<std::__1::__bind<void (WebKit::RemoteLayerTreeDrawingArea::*&)(), WebKit::RemoteLayerTreeDrawingArea*> >::call() 19 0x10d2f189b WTF::Function<void ()>::operator()() const 20 0x10d4f4739 WebCore::Timer::fired() 21 0x11b2e5c34 WebCore::ThreadTimers::sharedTimerFiredInternal() 22 0x11b2eddd1 WebCore::ThreadTimers::setSharedTimer(WebCore::SharedTimer*)::$_7::operator()() const 23 0x11b2edd89 WTF::Function<void ()>::CallableWrapper<WebCore::ThreadTimers::setSharedTimer(WebCore::SharedTimer*)::$_7>::call() 24 0x118e94b5b WTF::Function<void ()>::operator()() const 25 0x11b2c7955 WebCore::MainThreadSharedTimer::fired() 26 0x11b35d579 WebCore::timerFired(__CFRunLoopTimer*, void*) 27 0x10ac65374 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ 28 0x10ac65032 __CFRunLoopDoTimer 29 0x10ac64bea __CFRunLoopDoTimers 30 0x10ac5c604 __CFRunLoopRun 31 0x10ac5ba89 CFRunLoopRunSpecific LEAK: 3 WebPageProxy https://build.webkit.org/results/Apple%20iOS%2011%20Simulator%20Debug%20WK2%20(Tests)/r224023%20(645)/results.html
Reverted r223984 for reason: Caused LayoutTest assertion failures. Committed r224032: <https://trac.webkit.org/changeset/224032>
Re-landed with fixes: https://trac.webkit.org/r224078
Re-opened since this is blocked by bug 179026
The perf regression seems to happen because we're repainting all of the layers every frame now.
And that seems to happen because we take filter blur radius into account when computing layer bounds (bug 81239).
Ah, RenderLayerCompositor::cacheAcceleratedCompositingFlags() was calling setCompositingLayersNeedRebuild() every time because forceCompositingMode != m_forceCompositingMode
m_forceCompositingMode is flip-flopping between cacheAcceleratedCompositingFlags and cacheAcceleratedCompositingFlagsAfterLayout.
Created attachment 326824 [details] Patch
Comment on attachment 326824 [details] Patch Clearing flags on attachment: 326824 Committed r224796: <https://trac.webkit.org/changeset/224796>