Stealing Chromium: Embedding HTML5 with the Servo Browser Engine (LinuxCon NA 2014)
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Mike Blumenkrantz (Senior Engineer, Samsung Open Source Group), and Lars Bergstrom (Mozilla Research) share their research and implementation of HTML5 within the Servo Browser Engine.
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Stealing Chromium: Embedding HTML5 with the Servo Browser Engine (LinuxCon NA 2014)
- 1. STEALING CHROMIUM: EMBEDDING HTML5 WITH THE SERVO BROWSER ENGINE Lars Bergstrom Mozilla Research Mike Blumenkrantz Samsung R&D America
- 2. Why a new web engine? • Support new types of applications and new devices • All modern browser engines (Safari, Firefox, Chrome) originally designed pre-2000 • Coarse parallelism • Tightly coupled components • Vast majority of security issues are related to the C++ memory model
- 3. Servo •Written in a memory-safe systems language, Rust • Architected for parallelism • Coarse (per-tab), as in Chrome • Lightweight (intra-page), too • Designed for embedding
- 4. Rust - safe systems programming • C++ syntax and idioms • C++-like performance •Memory safety • Concurrency • Parallelism http://www.rust-lang.org
- 5. Familiar syntax and performance
- 6. Memory safety without overhead • Lifetimes and ownership ensure memory safety •No garbage collection •No reference counting •No C++ “smart” pointer classes
- 7. Example of code you can’t write
- 8. How a browser works HTML CSS JS Script & Interactions DOM Flow Tree Display Lists Script Layout Render Parsing More details: http://www.html5rocks.com/en/tutorials/internals/howbrowserswork/
- 9. How a browser works HTML CSS JS Script & Interactions DOM Flow Tree Display Lists Script Layout Render Parsing This works: <html> <script> document.write (“</script> <li>foo</li> </html> More details: http://www.html5rocks.com/en/tutorials/internals/howbrowserswork/
- 10. Timing breakdown Task Percentage Runtime libraries 25% Layout 22% Windowing 17% Script 16% Painting to screen 10% CSS styling 4% Other 6% Data from A Case for Parallelizing Web Pages. Mai, Tang, et. al. HOTPAR ‘12
- 13. Servo’s architecture Constellation Pipeline 1 (iframe 1) Renderer Script Layout Tab 1
- 14. Servo’s architecture Tab 1 Constellation Pipeline 1 (iframe 1) Renderer Script Layout Pipeline 2 (iframe 2) Renderer Script Layout
- 15. Servo’s architecture Tab 1 Constellation Pipeline 1 (iframe 1) Renderer Script Layout Pipeline 2 (iframe 2) Renderer Script Layout Pipeline 3 (iframe 3) Renderer Script Layout
- 16. Demo: parallelism and sandboxing
- 17. Parallel layout •Matters hugely on mobile platforms • Processors run at lower frequencies, but many cores •Would enable more complicated pages on all platforms • Implemented by work-stealing algorithm See: Fast and Parallel Webpage Layout. Meyerovich and Bodik. WWW 2010.
- 18. Parallel layout body div div div text bold text text
- 19. Parallel layout body div div div text bold text text Queue div div div
- 20. Parallel layout challenges •HTML layout has complex dependencies • Inline element positioning • Floating elements • Vertical text • Pagination • Considering adding speculation
- 21. Layout: parallel speedups Time (ms) 700 525 350 175 0 High CPU Frequency Low CPU Frequency 1 2 3 4 5 6 7 8 Number of Threads
- 22. Total time with parallel layout Time (s) 3.6 2.7 1.8 0.9 0 High CPU Frequency Low CPU Frequency 1 2 3 4 5 6 7 8 Number of Threads
- 23. Total power with parallel layout Power (J) 120 90 60 30 0 High CPU Frequency Low CPU Frequency 1 2 3 4 5 6 7 8 Number of Threads Measurements by Laleh Beni, intern from University of California Irvine
- 24. Punchline: parallelism for power, too • Force low-frequency CPU setting • Above four cores, same end-to-end performance as single core at high-frequency • BUT, 40% of the power usage • Could also parallelize more • Rendering, CSS selector matching, etc.
- 25. From engine to browser • Servo just renders pages • Similar to the Blink and Gecko engines • Designed to work in many browser shells • Firefox OS, over interprocess communication (IPC) • Android, by implementing a Java wrapper •On the desktop with…
- 26. What is embedding? •Hosting web engine in native application
- 27. Why embed? • Reduced development time •HTML5 popularity
- 28. How not to embed •WebKit • Blink • Both suffer from an unstable API • Application developer choices: • Ship full browser engine with application • Continually update to match breakages
- 29. How to embed? • CEF: Chromium Embedded Framework • Isolates application developers from core API • C API with C++ extensions
- 30. Servo embedding strategy • Stable API/ABI • Extensive API testing is a plus • C-based • Flexible • Already designed
- 31. How to embed with Servo? • Use CEF API+ABI • Removes need for YA embedding API • Less competition, more coding • Allows easy testing between engines • Servo: the pragmatic embedding engine
- 32. Servo embedding methodology • Full symbol/ABI coverage • Every CEF function call resolves to a Servo function • Struct allocation sizes are identical typedef struct _cef_string_utf8_t { char* str; size_t length; void (*dtor)(char* str); } cef_string_utf8_t; !!!!! C pub struct cef_string_utf8 { pub str: *mut u8, pub length: size_t, pub dtor: extern “C” fn(str: *mut u8), } !!!!! Rust
- 33. Servo embedding development • Start with base set of symbols • `nm -u` on CEF applications • Track function execution • CEF <-> Blink <-> Application <-> CEF … •Mimic CEF behavior using Servo equivalents • Use preload hacks to test • LD_PRELOAD on Linux
- 34. Servo status • Pass some tests • ACID1, ACID2 • Render basic web pages •Wikipedia, etc. • Focus on design + challenges • Parallelism, latency, power, memory
- 35. Servo roadmap • https://github.com/servo/servo/wiki/Roadmap • Q3 2014 •Writing modes (vertical text) •DOM memory usage, perf, and features •Web Platform Tests & CSS Ref Tests • Q4 2014 • Very basic dogfooding
- 36. Getting involved with Servo •www.github.com/servo/ servo/issues • Filter for “E-Easy” • irc.mozilla.org, #servo channel •Worldwide community • Looking for more partners and contributors • larsberg@mozilla.com