Published on October 19, 2013
Are Today’s Good Practices… Tomorrow’s Performance Anti-Patterns? @andydavies #VelocityConf, New York http://www.ﬂickr.com/photos/nzbuu/4093456029 Saturday, 19 October 13
What if … … dataURIs are an anti-pattern? http://www.ﬂickr.com/photos/willypayne/3116395089 Saturday, 19 October 13
The ‘humble’ dataURI url(data:image/ png;base64,iVBORw0KGgoAAAANSUh EUgAAABkAAAAZCAMAAADzN3VRAAAAG XRFWHRTb2Z0d2FyZQBBZG9iZSBJbWF nZVJlYWR5ccllPAAAAAZQTFRF/ wAAAAAAQaMSAwAAABJJREFUeNpiYBg Fo2AwAIAAAwACigABtnCV2AAAAABJR U5ErkJggg==) Saturday, 19 October 13 =
dataURIs for CSS images Makes a blocking resource larger by including non-blocking resources • Browser can’t start rendering page until CSS has downloaded * • Images don’t block Do they have the same caching lifetime? * Some browsers defer download of CSS when media query doesn’t match Saturday, 19 October 13
1. Take 50 icons 2. Create 50 stylesheets, each with one more dataURI than previous 3. Create matching HTML file for each stylesheet 4. Test them all! Saturday, 19 October 13
Larger CSS download == longer time to RenderStart RenderStart - TTFB (ms) 1000 875 750 625 500 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 Number of Sprites Saturday, 19 October 13
We have our rules… http://www.ﬂickr.com/photos/sowrey/2441134911 Saturday, 19 October 13
and we love recipes… http://www.ﬂickr.com/photos/mrsmagic/2247364228 Saturday, 19 October 13
But, what happens when things change? Saturday, 19 October 13
Browsers already use the network differently Saturday, 19 October 13
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New network protocols are coming here http://www.ﬂickr.com/photos/jonlachance/3427660741 Saturday, 19 October 13
Differences in TCP Connection Use HTTP 1.1 SPDY Saturday, 19 October 13
New Standards - opportunities and challenges Saturday, 19 October 13
74% of visitors support async attribute <script async src="myscript.js"><script> http://caniuse.com/script-async Saturday, 19 October 13
XSS Saturday, 19 October 13
Content-Security-Policy “Content Security Policy, a mechanism web applications can use to mitigate a broad class of content injection vulnerabilities, such as cross-site scripting (XSS)” http://www.w3.org/TR/CSP/ Saturday, 19 October 13
Example Only allow scripts to be executed if they come from a designated host, disables inline scripts by default. Content-Security-Policy: script-src http://www.site.com Can re-enable inline scripts, but increases XSS risk Content-Security-Policy script-src 'self' Saturday, 19 October 13
What other performance enhancements do we rely on JS for? Guardian split page into - Content - Enhancements - Leftovers Others rely on scroll handlers for lazyload Saturday, 19 October 13
Tested some scenarios, measured the outcomes http://www.ﬂickr.com/photos/chandramarsono/4324373384 Saturday, 19 October 13
Test Environment - EC2 - Medium Instance - Dublin - Apache 2.2 - GZIP - Keep-Alive - mod_pagespeed - mod_spdy - WepPageTest, Saturday, 19 October 13 Dulles / Chrome / Cable
Off the shelf website template http://www.html5xcss3.com/2012/05/html5-template-interio.html Saturday, 19 October 13
Minimal Optimisations - HTTP 1.1 vs SPDY 0s 1s 2s 3s 4s HTTP SPDY SPDY is faster (GZIP / Keep-Alive / initcwnd 10) Saturday, 19 October 13 5s 6s
Waterfall for HTTP Test Saturday, 19 October 13
Waterfall for SPDY Test Saturday, 19 October 13
So which rules are most likely to be at risk? - Split dominant content domains - Reduce requests - Merging - Sprites - DataURIs Saturday, 19 October 13
Sharding CSS background: url() images 0s 1s 2s 3s 4s 5s Sharded Not Sharded Sharded page is much slower Saturday, 19 October 13 6s 7s 8s
Connection to shard opened later New TCP connection opened Saturday, 19 October 13
New connection shouldn’t have been opened “Both chrome and ﬁrefox will automatically unshard transparently for you when using spdy and both of the sharded hosts are at the same IP address and covered under one SSL cert (e.g. *.example.com).” Patrick McManus, Mozilla http://www.stevesouders.com/blog/2013/09/05/domain-sharding-revisited/#comment-60146 Saturday, 19 October 13
Sharding <img src= 0s 1s 2s 3s 4s 5s 6s Sharded Not Sharded Sharded page is marginally faster??? Saturday, 19 October 13 7s 8s
Other tests carried out - Sharding JS / CSS Horrible - Merging CSS Slower - Server Push No noticable difference - jQuery from Google CDN Suprisingly quick Saturday, 19 October 13
It’s only going to get more complex “Situational Performance Optimization, The Next Frontier” Guy Podjarny http://www.ﬂickr.com/photos/freshwater2006/693945631 Saturday, 19 October 13
Hmm… How do we move forward? http://www.ﬂickr.com/photos/atoach/6014917153 Saturday, 19 October 13
Will complexity lead to the end of hand crafted optimisations? http://www.ﬂickr.com/photos/simeon_barkas/2557059247 Saturday, 19 October 13
Start experimenting http://www.ﬂickr.com/photos/giosp/3933753363 Saturday, 19 October 13
Need to improve our toolkit http://www.ﬂickr.com/photos/alexander/1146677 Saturday, 19 October 13
Limits to what protocols or automation can fix Requests by Domain Saturday, 19 October 13 Bytes by Domain
Thank You! @andydavies email@example.com http://slideshare.net/andydavies http://www.ﬂickr.com/photos/nzbuu/4093456029 Saturday, 19 October 13
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