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Android Chromium Rendering Pipeline
이형욱 (hyungwook.lee@navercorp.com)
시스템스컴퓨팅G / NAVER LABS
2015-04
2
0. Contents
Chapter 1: 브라우저 렌더링에서의 Critical Path란 무엇인가?① Summary of browser’s main flows② HTML Parser③ JavaScriptEngine④ Render Tree, Layout⑤ Rendering Pipeline Runs on Main Thread⑥ New Rendering Model⑦ GPU Accelerated Compositing
Chapter 2: Chromium은렌더링성능향상을위하여…① Chrome Vs Chromium② Why Multi Process Architecture?③ GPU Process④ Multi Threads Models in Renderer Process⑤ Chromium Scheduler: Right things right time
Chapter 3: Chromium-powered Android WebView① What is Android WebView? ② Android WebView Version History ③ Chromium Powered WebView Structure ④ Chrome Vs Android Rendering model ⑤ Chrome Vs Chromium WebView⑥ Chromium WebView Rendering Pipeline⑦ The Future of WebView?
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Chapter 1, 브라우저 렌더링에
서의 Critical Path란 무엇인가?
4
<html><head>
<title> NAVER </title></head><body>
<div><h1> Hello </h1><p> World </p>
</div></body>
</html>
1. Summary of browser main flows.
[Source: How browsers work]
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HEAD
TITLE
NAVER
BODY
DIV
H1 P
HTML
Hello World
<html><head>
<title> NAVER </title></head><body>
<div><h1> Hello </h1><p> World </p>
</div></body>
</html>
2. HTML Parser
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3. Java Script Engine
Source Code Parser Syntax Tree
BytecodeGenerator
Bytecode
JIT Compiler Machine Code
Execution
Loader
Parser
DOM
Java Script
HTML DOM API
Evaluate
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HTML
CSS
DOMTree
StyleRules
RendererTreeLookup
4. Render Tree Creation
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HEAD
TITLE
NAVER
BODY
DIV
H1 P
HTML
Hello World
Block
Block
Block
Block Block
Inline Inline
5. Render Tree
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6. Layout
HEAD
TITLE
NAVER
BODY
DIV
H1 P
HTML
Hello World
Block
Block
Block
Block Block
Inline Inline
(0, 0, 1024, 768)
(0, 0, 1024, 768)
(0, 0, 1024, 55)
(10, 20, 1024, 37) (10, 80, 1024, 18)
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7. Rendering
Block (html)
Block (body)
Block (div)
Block (h1) Block (p)
Inline (hello) Inline (world)
(0, 0, 1024, 768)
(0, 0, 1024, 768)
(0, 0, 1024, 55)
(10, 20, 1024, 37) (10, 80, 1024, 18) 1024
768<div>
11
8. Rendering Pipeline Runs on Main Thread
[Source: Blink Rendering Pipeline]
[Source: Chrome Graphics - BlinkOn 1]
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9. New Rendering Model: Layers (1/4)
[Source: WebKit.org]
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9. New Rendering Model: Layers (2/4)
1. Avoid unnecessary repainting- If yellow and red have their own layers, then nothing needs"repainting" while this example animates.
2. Makes some features more efficient or practical- Including: Scrolling, 3D CSS(translate3d, …), opacity, filters, WebGL, etc.
[Source: Compositing in Blink and WebKit]
14
9. New Rendering Model: Layers (3/4)
1. It's the root object for the page. <html>
2. CSS position properties (relative, absolute)
3. Has overflow, an alpha mask or reflection
4. CSS filter
5. CSS 3D Transform , Animations
6. <canvas>, <video>
7. will-change (Chrome 36, Firefox 36, Opera 24)
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Cost of Multi Layers: Memory, Computing
<Layer를 너무 많이 사용할 경우 Compositing 시간이 오래 걸림>
9. New Rendering Model: Layers (4/4)
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10. GPU Accelerated Compositing
1. 각 Layer 별 bitmap을 생성 (Render Layer traversing)
2. Text와 Image는 CPU에서 Rasterization
3. Textures upload into Video memory
4. Compositor에서 Layer 순서에 맞게 Texture를 drawing하여 화면에 Update
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Chapter 2, Chromium은 렌더
링 성능 향상을 위하여 어떤 기
술들을 사용하고 있는가?
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Google Chrome Chromium
Logo Colorful Blue
Crash reporting Yes, if you turn it on None
User metrics Yes, if you turn it on No
Video and audio tags AAC, MP3, Vorbis and Theora Vorbis and Theora by default
Adobe Flashcustom (non-free) plugin included in release
supports NPAPI plugins, including the one from Adobe
PDF supportcustom (non-free) plugin included in release
downloads and displays with system PDF viewer
Code Tested by Chrome developersMay be modified by distributions
Sandbox Always on Depending on the distribution
Quality AssuranceNew releases are tested before sending to users
Depending on the distribution
1. Chrome Vs Chromium
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2. Why Multi Process Architecture?
기존 브라우저의 문제점
• 현재(크롬 제작 당시)의 브라우저는 과거의 OS와 비슷한 구조
• 과거의 OS는 단일 사용자, 협조적 멀티 태스킹 시스템
• 이와 같은 시스템에서, 어떤 어플리케이션의 문제는 OS 전체의 안정성에 영향을 미침
• 단일 프로세스 모델의 브라우저에서는 한 페이지의 문제가 브라우저 전체에 문제를 일으킴
문제해결을 위한 접근
• 절대적으로 안정적인 렌더링 엔진을 만드는 것은 거의 불가능함
• 최근의 OS는 각 어플리케이션을 고립시킴으로써 특정 어플리케이션의 문제가 시스템 전체의 안정
성에 영향을 미치지 않도록 하며, 사용자 각자의 데이터를 보호하고 있음
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3. Chromium Rendering Pipeline
[Source: Chrome Graphics - BlinkOn 1]
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• GPU Process의 구조적 특징: Security, Robustness, Uniformity, Parallelism
• Client(Render Process): GL Command를 생성, Ring Buffer에 Insert
-> 일반적인 페이지의 경우 Texture Upload용으로 사용, HTML5 Canvas / WebGL은 직접 GL Command를 사용
• Server(GPU Process): Command를 fetch, execution.
• GL command는 GL ES 2.0 API와 거의 유사한 Async command
4. GPU Process
[Source: GPU Accelerated Compositing in Chrome]
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5. Multi Threads: Main Thread Rendering
[Source: Chrome Graphics - BlinkOn 1]
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5. Multi Threads: Threaded Compositor
[Source: Chrome Graphics - BlinkOn 1]
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5. Multi Threads: Threaded Rasterization
[Source: Chrome Graphics - BlinkOn 1]
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6. Skia’s SkPicture Canvas
A modern 2D graphics library
SkPicture, SkPicturePlayBack:Records and replay draw operations.
[http://www.dorothybrowser.com/parallelizing-canvas-rendering/]
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7. Chromium Rendering Pipeline in detail
1. Record 2. Raster 2.5 Upload 3. Composite
updaterecord
ThreadProxy
updaterecordPicture
Layer
updatePictureLayerImpl
Raster
LayerTreeHost
updaterecordupdate
recordGraphicsLayer
Blink LayerTreeHostImpl
Proxy
Main Thread Compositor Thread Raster Threads
Call into WebKitwhich calls Skia
SkPicture recordsthe paint for deferred raster
Decode images In parallel
Raster into shared memory
Send to GPU process using custom extensionGPU process doesglTexImage2dasynchronously
Send draw cmdsTo GPU Processover command bufferglBindTextureglDrawElements
Main Thread Raster Thread Compositor Thread
Tree Sync
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8. Chromium Scheduler: Right things right time
1. Record
3. Raster
4. Upload
5. Composite
2. Tree Sync
6. SwapBuffer
Scheduler
BeginFrame
Commit Pending
Tree
Draw& Swap Buffer
UpdateVisibleTiles
<StateMachine in Compositor Threads>
ActivatePending
Tree
VSync
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Renderer Process
Cache Thread File Thread DB Thread IO Thread
I/O Thread
Browser Process
Main Thread
Renderer Process
IPC
RenderView
RenderWidget
Blink
RenderView
RenderWidget RenderWidget
Blink Blink
RenderView
WebContentsRenderViewHost
ManagerRenderViewHost
RenderWidgetHost
RenderViewHost
RenderWidgetHost
RenderViewHost
RenderWidgetHost
SiteInstance RenderProcessHost
SiteInstance RenderProcessHost
Main ThreadMain Thread
WebContentsRenderViewHost
Manager
RenderMainThread(Single Process Mode)
1
2
3
4
5
6 Compositor
GPU Thread(Android)
Process LauncherThread
Raster
I/O Thread
Compositor
Raster
9. Chromium Architecture in detail
29
Chapter 3, Android Chrome과
Chromium-powered WebView
의 구조적 차이는 무엇인가?
30
1. What is Android WebView?
Web content in a box:- Powers browsers such as AOSP Browser- Displays almost all mobile banner ads- Can be used to create portable HTML-based apps- Often intermixed imperceptibly with native Views
<- Android View
<- Android WebView
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2. Android WebView Version History
Android <= J: custom WebKit-based “classic” WebViewAndroid K: Chromium 30 / 33-based WebViewAndroid L: Unbundled Evergreen WebView
http://com.odroid.com/sigong/nf_file_board/nfile_board_view.php?keyword=&tag=ODROID-U3&bid=214
http://www.ibtimes.co.uk/moto-g-finally-tastes-android-5-0-lollipop-via-cyanogenmod-12-unofficial-build-1475895
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3. Chromium Powered WebView Structure
Blink(WebKit)
Content (Multi-process-impl)
Content API
Blin
k
Ch
rom
ium
Android WebView
Framework
Chrome Browser
Framework
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4. Chrome Vs Android Rendering Model
Make main thread free
Make sure contents on time
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5. Chrome Vs Chromium WebView
ChromeMulti-process UI thread GPU thread Texture upload thread Per renderer process:
o Blink threado CC impl threado Raster thread
Chromium Scheduler
SurfaceView
Chromium WebViewSingle-process Combined UI + renderer CC thread Android RenderThread (+in-proces
s GPU thread) Canvas/WebGL GPU thread Blink thread Raster thread
Android Rendering Scheduer
Draw functor (Private API)
[Source: Android WebView rendering BlinkOn 3]
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6. Accelerated Android Rendering
[Source: http://www.slideshare.net/deview/1d6review-of-android-l-developer-preview]
[Main
Th
read
]
36
7. Chromium WebView Rendering Pipeline in K
DrawGLFunction()Synchronous Compositor
ViewRootImplperformDraw()
ViewDraw(Canvas)
ViewonDraw(Canvas)
HardwareCanvasdraw*(…,Paint)
WebView::onDraw()Set draw functor via DrawGLFunctor::requestDrawGL()
(canvas.callDrawGLFunction(mNativeDrawGLFunctor))
3. Composite
Chromium WebView
1. Record 2. Raster
Main
Blink Thread Raster Threads Main Thread
37
8. Chromium WebView Rendering Pipeline in L
WebView::onDraw()1. Set draw functor2. Request Record & Raster
Synchronous Compositor
ViewonDraw(Canvas)
HardwareCanvasdraw*(…,Paint)
Chromium WebView
1. Record 2. Raster
Main
Raster Threads
ViewRootImplperformDraw()
Ren
der
Blink Thread
DrawGLFunction()Synchronous Compositor
3. Composite
Render Thread
38
9. Android Chromium WebView Architecture
Blink Thread Cache Thread File Thread DB Thread IO Thread
Main Thread
IPC
WebContentsRenderViewHost
ManagerRenderViewHost
RenderWidgetHost
RenderViewHost
RenderWidgetHost
RenderViewHost
RenderWidgetHost
SiteInstance RenderProcessHost
SiteInstance RenderProcessHost
Chromium WebView’s Process
RenderView
RenderWidget
Blink
Process LauncherThread
Raster Thread
WebView
39
10. The Future of WebView?
“Under active debate at the moment” (2014/11)
1. Opposing use cases1) WebView as a browser-in-a-box, Vs2) WebView as one tool in a hybrid app toolset
2. Opposing update priorities1) App developers want the latest features and
performance improvements2) They also want stability to the point of bug-for-bug
compatibility
[Source: Android WebView rendering BlinkOn 3]
40
Appendix #1: References
1. http://www.w3.org/TR/CSS2/
2. http://www.w3.org/TR/DOM-Level-2-Core/core.html
3. http://www.html5rocks.com/en/tutorials/internals/howbrowserswork/
4. http://deview.kr/2013/detail.nhn?topicSeq=5
5. http://www.slideshare.net/joone/hardware-acceleration-in-webkit
6. http://dev.chromium.org/developers/design-documents/multi-process-architecture
7. https://docs.google.com/a/chromium.org/presentation/d/1pYAGn2AYJ7neFDlDZ9DmL
HpwMIskzMUXjFXYR7yfUko/edit
8. http://dev.chromium.org/developers/design-documents/inter-process-communication
9. http://dev.chromium.org/developers/design-documents/multi-process-resource-
loading
10. http://dev.chromium.org/developers/design-documents/gpu-accelerated-
compositing-in-chrome
11. http://dev.chromium.org/developers/design-documents/compositor-thread-
architecture
12. http://dev.chromium.org/developers/design-documents/impl-side-painting
13. http://blog.csdn.net/jaylinzhou/article/details/18313505
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