Performance analysisclass

The Art and Science of Web Performance Daniel Austin Technical Staff Paypal, Inc.CMU Invited LectureAugust 02 , 2012 daaustin@paypal.comV1.1 @daniel_b_austin

TODAY’S PROGRAMOverture: Web Performance As Art And ScienceFirst the Theory……Then the PracticeCoda: Making the Web Faster and Smarter Confidential and Proprietary 8/2/2012

STATE OF THE ART?• An Art and a Science• Very Little Prior Art• Users Suffer – • The World Wide Wait isn’t over yet!• Rapid Change in the Industry • Browsers • Devices • Standards• The Rest of the World is Catching Up • Challenges of Global/Local/Mobile/Social Performance Confidential and Proprietary 8/2/2012

PERFORMANCE IS RESPONSE TIME PERFORMANCE IS RESPONSE TIME PERFORMANCE IS RESPONSE TIME PERFORMANCE IS RESPONSE TIME(It’s not latency, it’s not bandwidth, it’s not queue residence time or queue length or any such thing.) Confidential and Proprietary 8/2/2012

Who needs ‘Performance’ measurements anyway?? Confidential and Proprietary

A MORE RATIONAL APPROACH? Confidential and Proprietary

DIMENSIONS OF PERFORMANCE• Geography/Network location• Bandwidth/Transport Type• Browser/Device Type • RT Varies by as much as 50%• Page Composition • Client-side rendering and execution effects (JS, CSS) • Network Transport Effects • # of Connections, CDN Use Confidential and Proprietary 8/2/2012

THE MPPC MODEL OF WEB PERFORMANCE “Multiple Parallel Persistent Connections” Request DNS/Network Initiation by HTTP Request Resolution HTTP Request User t1 This entire cycle, steps 1-4, is repeated once for each external Page reference on the page, so for a given page the total time is: Composition S T = S Dt1 + Dt2 + Dt3 + Dt4 t2 n+1 n+1End User Where n is the number of external page requisites. Payload Browser HTTP Response Delivery Time HTTP Response Rendering Time t3 t4 T1 T2 T3 T4 Connection Time Server Duration Transport Time Render Time Confidential and Proprietary 8/2/2012

HTTP CONNECTION FLOW Client Server Connection setup (t1) Handshake time Request transmissionClient’s perceived timeresponse time Request (t2) Estimated server processing time Response transmission Response (t3) time The more HTTP requests & network roundtrips you require, the slower your site will be: Images, CSS, JS, DNS lookups, Redirects, #of packets Confidential and Proprietary 8/2/2012

T1 – MAKING THE CONNECTION 1= DNS + TCP+ SSL Confidential and Proprietary 8/2/2012

T2 – THE SERVER DURATION • Let ( ) r • U = ( r)[ r W] • X =U* • Navg = ( r [W( r)W+1 - (W+1)( r)W+1] • … so 2 = Navg/X (The response time law)Never mind - it’s a constant! Confidential and Proprietary 8/2/2012

T3 – TCP TRANSPORT TIMESingle Object: 3 = Sz/R+2RTT+ idleFor persistent parallel connections: 3 = (M+1)Si/Ri+[M/kNh]*3 RTTi+ idle… for 1 base HTML page with M objects, with Sibits, at bandwidth Ri, k connections perhost, and Nh unique hostnames Confidential and Proprietary 8/2/2012

T4 – WHAT THE BROWSER DOES Confidential and Proprietary 8/2/2012

BANDWIDTH EFFICIENCY Bmax = 1.22*(L)^1/2 * MSS/RTT Confidential and Proprietary 8/2/2012

WHERE ARE THE DELAYS? Confidential and Proprietary 8/2/2012

LET’S TALK TOOLSSite Performance Services Page Analysis Tools – Gomez – YSlow – Keynote – MS Virtual RoundTrip – WebPagestest.Org Analyzer,• ‘Wholesale’ Testing HTTPWatch, Many Others – Statistical data for many page views under different – F12 in your browser conditions • ‘Retail’ Testing – Operational testing – One Page or App – Best for understanding – Diagnostic global and network effects – Best for functional testing Confidential and Proprietary

COMMERCIAL TESTING SERVICES• Gomez, AlertSite, and Keynote toolsets are similar in many ways • Synthetic Test Setup • Test nodes in large datacenters and/or end user’s machines • Statistical data about response times• You can do this for yourself on a smaller scale at WebPageTest.org Confidential and Proprietary 8/2/2012

HAPPY BIRTHDAY, YSLOW!Methodology – DOM Crawler and Packet Sniffer – More accurate – Analyzes components – Stats viewImplements the 14 18 22 105 YSlow Rules – All browsers except IE – Mobile bookmarklet – Best tool for page analysis Confidential and Proprietary

TESTING YOUR COMPETITORS FOR FUN &PROFIT • Try to measure task sequences not pages • Be prepared for lots of breakage • Be respectful • Difficult and time-consuming Confidential and Proprietary 8/2/2012

TASK-BASED PERFORMANCE THINKING Welcome 1400 Inbox 2200 Inbox Bulk 3200 (B) … 61.77% P(A,B) = 0.5168 Read 10.04% 66.25% Message (D) Verify (F) 34.52% Welcome 9.85% Bulk (A) (C) 58.07% 64.53% 22.30% 34.38% 35.02% Send Compose28.04% Confirm (E) (G) Confidential and Proprietary 8/2/2012

GLOBAL PERFORMANCE TESTING (BRIEFLY)• Cannot compare performance data out-of-region• There are many global factors involved in performance: • Bandwidth • ISP • Infrastructure • Secular cycles (weeks, holidays, usage patterns)• The best approach: use the relative ‘StormCat’ system • Best case (Northern California high broadband @3 AM) • Worst Case (rural Indonesia on VSNL @ 2PM local) • Divide the range into 5 categories equally spaced between the best & worst: some locales will be in Cat I, some in Cat II, some in Cat III, etc. Confidential and Proprietary 8/2/2012

BAKE IT IN UP FRONTPerformance Engineering is adesign-time activity!This is absolutely crucial!Anti-Pattern: Releasing anew or modified productwithout testing itsperformance.Seriously. Confidential and Proprietary

QUANTIFY Confidential and Proprietary

KNOW THE LANDSCAPE “What are the differences among browsers?” “What are my competitors doing?” “What about low bandwidth users? “How can I test that?” Confidential and Proprietary 8/2/2012

THE 7 HABITS OF EXCEPTIONALPERFORMANCE 1. Make Performance a Priority 2. Test, Measure, Test Again 3. Learn about the Tools 4. Balance Performance with Features 5. Track Results Over Time 6. Set Targets 7. Ask Questions; Check It for Yourself! Confidential and Proprietary

CODA: MAKING THE WEB SMARTER ANDFASTER• Faster HTTP • SPDY • HTTP Speed+Mobility • Scratch• Better Browsers • Chrome has disrupted the market • HTML5 will drive further evolution• Moving to Mobile/Device Platforms • More sensitive to network effects of all kinds • Application-driven user experience • Moving away from Hypertext? Confidential and Proprietary 8/2/2012

42Michael Faraday is the father of network performance, havingperformed the first bandwidth measurements on the firsttransatlantic telegraph cable in 1854. Daniel Austin Technical Staff CMU Invited Lecture Paypal, Inc. August 02 , 2012 V1.1 daaustin@paypal.com @daniel_b_austin

Performance analysisclass

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