Frontend Performance: Beginner to Expert to Insanity

https://confoo.ca/en/2016/session/frontend-performance-beginner-to-expert-to-insanity

Transcript

1. FrontEnd Performance Beginner to Expert to Insanity
2. Philip Tellis @bluesmoon http://tech.bluesmoon.info http://www.soasta.com/mpulse/
3. Get the most benefit with the least effort
4. 0 Start with a really slow site
5. 0.1 Start Measuring
6. Or use RUM for real user data (boomerang/mPulse)
7. • Pre-gzip static assets (gzip_static in nginx) • eg: foo.js.gz is served if Accept-Encoding: gzip is included • For dynamic content, use chunked transfers with gzipped chunks • You can do this by flushing buffers on the server 0.2 enable gzip http://www.slideshare.net/billwscott/improving-netflix-performance-experience
8. • Understand newer compression formats like ZopFli, Brotli, and WebP. • But also understand the trade-off between better compression and complexity of image decoding on mobile devices 0.2 enable gzip… and compression http://google-opensource.blogspot.ca/2015/09/introducing-brotli-new-compression.html http://blog.codinghorror.com/zopfli-optimization-literally-free-bandwidth/ https://developers.google.com/speed/webp/
9. 0.3 Cache Cache-control: public, max-age=31415926 Do NOT set LastModified or ETags headers to avoid conditional requests
10. 0 Congratulations You’ve just been promoted!
11. 1 What the Experts do
12. 1.1 CDN • Serve your root domain through a CDN • And make sure your CSS is on the same domain • Chrome opens two TCP connections to the primary host, the second one is "just in case" http://www.jonathanklein.net/2014/02/revisiting-cookieless-domain.html
13. 1.1 Google Chrome will open two TCP connections to the primary host, one for the page, and the second "just in case"
14. 1.1 Don’t waste it
15. 1.2 Split JavaScript • Critical: in the HEAD • Enhancements: loaded async • Flush buffers after the HEAD • for HTTP/2, these would have different priorities
16. 1.3 Parallelize downloads… or maybe don’t • You can have more bandwidth, but you cannot have lower latency • For HTTP/1.1, mitigate latency effects by parallelizing across multiple TCP sockets • But with HTTP/2, this rule is turned on its head since multiplexing and pipelining is built in http://www.soasta.com/blog/more-bandwidth-isnt-a-magic-bullet-for-web-performance/
17. 1.4 Flush Early and Often • avoid TCP Slow Start, • speed up CSS • Help the browser’s lookahead parser Getting bytes to the client ASAP will:
18. TCP Handshake & Congestion Control
19. 1.5 Increase initcwnd Initial Congestion Window: Number of packets to send before waiting for an ACK http://www.cdnplanet.com/blog/tune-tcp-initcwnd-for-optimum-performance/
20. 1.5 Increase initcwnd @mobtec on Twitter
21. 1.5b Also… net.ipv4.tcp_slow_start_after_idle=0 http://www.lognormal.com/blog/2012/09/27/linux-tcpip-tuning/
22. 1.6 PageSpeed mod_pagespeed and ngx_pagespeed
23. 1.7 Don’t just FastClick • FastClick fires a Click onTouchEnd • It might be better to initiate a TCP connect onTouchStart and fetch content normally onClick • Load a 0 byte image from the domain to do this, or use <link rel=“preconnect”>
24. 1.8 Use UserTiming to measure your code • The UserTiming API allows you to set performance timeline marks within your code • performance.mark("name") • performance.measure("name",
 "start_mark", "end_mark") http://www.html5rocks.com/en/tutorials/webperformance/usertiming/
25. 1.9 Avoid Pre-flighted XHR • Make sure any JS Library you use doesn’t automatically add an X-Requested-With header http://www.soasta.com/blog/options-web-performance-with-single-page-applications/
26. Relax https://www.flickr.com/photos/29825916@N05/5760905069/
27. 2 Things are gonna get insane!
28. Sort in ascending order of signal latency • Electrons through copper • Light through fibre • Pulsars • Station Wagons • Smoke Signals
29. Sort in ascending order of signal latency 1.Pulsars (light through vacuum) 2.Smoke Signals (light through air) 3.Electrons through copper / Light through fibre 4.Station Wagons (possibly highest bandwidth)
30. 2.0 Bandwidth is different around the world
31. 2.0 As are people
32. 2.0 Study real user data Look for potential places to parallelize, predict and cache
33. 2.1 Use RUM to determine optimum POP location • Use RUM to measure latency from user to multiple POPs • Pick POP based on lowest latency • Adapt to changes in network topology http://www.slideshare.net/rmaheshw/velocity-2015-pops-and-rum
34. 2.1 Use RUM to determine best CDN • Use RUM to measure latency from user to multiple CDN providers • Dynamically pick CDN based on what works best
35. 2.2 pre-browsing <link rel="prerender" href="url"> <link rel="preload" href=“url" as="type"> <link rel="dns-prefetch" href=“url"> <link rel="preconnect" href="url"> https://w3c.github.io/resource-hints/ http://w3c.github.io/preload/
36. 2.2 <link rel=“dns-prefetch”> • Does a DNS lookup for hostname mentioned in URL • This could help reduce latency when the request shows up — for first page views at least • Your DNS TTL needs to be long enough to survive past a page load
37. 2.2 <link rel=“preload”> • Tells the parser that this resource will be required later on • Browser can start downloading in the background if it has nothing better to do with its resources • no-cache header only applies to subsequent pages
38. 2.2 <link rel=“preconnect”> • Tells the browser to open a TCP connection to this host, and hold on to it • Any CORS restrictions will apply to this connection
39. 2.2 <link rel=“prerender”> • Tells the parser that this page is likely to be requested by the user • Browser downloads page, and all its resources, renders it, executes JavaScript and fires the onload event. • It’s like opening the page in a hidden Tab
40. 2.2 <link rel=“prerender”> • When user follows the URL, the page just shows up (< 5ms latency) • This is actually faster than switching tabs in the browser • The onVisibilityChange event fires and visibilityState changes from “prerender” to “visible” or “hidden”
41. 2.2 <link rel=“prerender”> — Caveats • The page needs to be requested using GET • The page should not require Authentication (401 response) • Prerender will be aborted if cookies, or localStorage change, or if the prerendered page has non-idempotent components
42. 2.2 onVisibilityChange And while you’re at it, don’t do expensive work if the page is hidden https://developer.mozilla.org/en-US/docs/Web/Guide/User_experience/ Using_the_Page_Visibility_API
43. 2.3 Post-load Fetch optional assets after onload
44. 2.4 Detect broken accept-encoding Many Windows anti-viruses and firewalls disable gzip by munging the Accept-Encoding header http://www.lognormal.com/blog/2012/08/17/accept-encoding-stats/
45. 2.5 HTTP/2 • Only one TCP connection per host • Do NOT use domain sharding • Do NOT use sprites • Do use Stream Multiplexing with Priorities • Do use Server Push http://chimera.labs.oreilly.com/books/1230000000545/ch12.html
46. — Tim Kadlec “4:2:0 subsampling of JPEGs gets a 62.5% memory savings” 2.6 Use 4:2:0 Chroma Subsampling Chroma Subsampling takes advantage of the fact that the human visual system is less sensitive to changes in colour than luminance http://en.wikipedia.org/wiki/Chroma_subsampling
47. 2.7 Resize Images for target Device Dimensions Resizing Images for specific screen sizes could be the difference between 1.5s and 30ms https://speakerdeck.com/tkadlec/mobile-image-processing-at-velocity-sc-2015
48. 2.8 Don’t force layout operations • DOM manipulations followed by a read of invalidated properties forces a layout • This has a huge CPU impact • Read before write • Batch update • Move operations into the HEAD Amiya Gupta @ Velocity 2015
49. 2.9 Understand 3PoFs Use blackhole.webpagetest.org to test for 3rd party single points of failure http://blog.patrickmeenan.com/2011/10/testing-for-frontend-spof.html
50. 2.9 3PoFs Request Map by Simon Hearne
51. 2.10 Understand the Iframe Loader Technique Take required but non-critical assets out of the critical path http://www.lognormal.com/blog/2012/12/12/the-script-loader-pattern/
52. 2.11 Understand your SpeedIndex http://heatmap.webperf.tools/render/150611_88_af4b9ceaa938f1b4647ff2e8ed41b550/10000
53. 2.12 What does your site cost? http://whatdoesmysitecost.com/test/150611_N5_9495f479626f6589299f62e440724064
54. 2.13 Prioritize optimizations based on user impact Conversion Impact Score in mPulse DSWB
55. 2.14 Become a WebPageTest power user • Check out the comparison view • Collect packet captures • Use Wireshark • Test out different network types
56. References • WebPageTest — http://webpagetest.org • Boomerang — http://www.lognormal.com/boomerang/doc/ • SOASTA mPulse — http://www.soasta.com/mpulse • Netflix gzip study — http://www.slideshare.net/billwscott/improving-netflix-performance-experience • Nginx gzip_static — http://wiki.nginx.org/HttpGzipStaticModule • ImageOptim — http://imageoptim.com/ • uncss — https://github.com/giakki/uncss • grunt-uncss — https://github.com/addyosmani/grunt-uncss • Caching — http://www.mnot.net/cache_docs/ • Same domain CSS — http://www.jonathanklein.net/2014/02/revisiting-cookieless-domain.html • initcwnd — http://www.cdnplanet.com/blog/tune-tcp-initcwnd-for-optimum-performance/ • Linux TCP Tuning — http://www.lognormal.com/blog/2012/09/27/linux-tcpip-tuning/ • Prerender — https://developers.google.com/chrome/whitepapers/prerender • DNS prefetching — https://developer.mozilla.org/en-US/docs/Controlling_DNS_prefetching • Subresource — http://www.chromium.org/spdy/link-headers-and-server-hint/link-rel-subresource • FE SPoF — http://blog.patrickmeenan.com/2011/10/testing-for-frontend-spof.html • Page Visibility API — https://developer.mozilla.org/en-US/docs/Web/Guide/User_experience/Using_the_Page_Vis... • HTTP/2 — http://chimera.labs.oreilly.com/books/1230000000545/ch12.html • More Bandwidth is not a Magic Bullet — http://performancebeacon.com/more-bandwidth-isnt-a-magic-bullet-for... • The UserTiming API — http://www.html5rocks.com/en/tutorials/webperformance/usertiming/ • The 3.5s dash for attention — http://www.slideshare.net/buddybrewer/the-35s-dash-for-attention-and-other-stuff-we-... • POPs & RUM — http://www.slideshare.net/rmaheshw/velocity-2015-pops-and-rum • Optimizing Images for Mobile — https://speakerdeck.com/tkadlec/mobile-image-processing-at-velocity-sc-2015 • Optimizing the MSN Homepage — Amiya Gupta @ Velocity 2015 • Simon Hearne’s Webperf Tools — http://requestmap.webperf.tools and http://heatmap.webperf.tools • What does my site cost — http://whatdoesmysitecost.com
57. Thank You
58. Philip Tellis @bluesmoon http://tech.bluesmoon.info http://www.soasta.com/mpulse/
59. Image Credits • Apple Pie
 http://www.flickr.com/photos/24609729@N00/3353226142/ • Puppies 7 weeks
 https://www.flickr.com/photos/29825916@N05/5760905069/