Caching for Cash - Part 4

Caching For Cash php|tek – Chicago, May 2009

80% of response time is spent downloading content

“ It all depends on how we look at things, and not how they are in themselves.” - Carl G. Jung

Key factor in performance Fewer HTTP Requests Easy to improve on

Sent with static content Slow upstream speed Big cookies

Cookie Size Response Time (Delta) 0 bytes 78 ms ( 0 ms ) 500 bytes 79 ms ( +1 ms ) 1000 bytes 94 ms ( +16 ms ) 1500 bytes 109 ms ( +31 ms ) 2000 bytes 125 ms ( +47 ms ) 2500 bytes 141 ms ( +63 ms ) 3000 bytes 156 ms ( +78 ms ) Times are for page loads on DSL (~800 kbps).

Eliminate unnecessary cookies Keep sizes low Appropriate domain levels Set Expires date appropriately

Be aware of max connection limits in browsers CNAME to point multiple sub domains to the same IP

One domain = 2 Parallel connections

Two domains = 4 Parallel connections

Too many hostnames can cause complications 2 – 4 sub domains is a good average

Combining 6 scripts into 1 eliminates 5 requests Challenges:
develop as separate modules
combinations vs. loading more than needed

JS does not comply with the parallel downloading rule

script defer attribute is not a solution
blocks rendering and downloads in FF
slight blocking in IE
Solution: move them as low in the page as possible

Crushes the files Strips out all cruft Voodoo magic

JSMin Dojo Shrinksafe Packer YUI Compressor http://short.ie/compression-rates

You can affect users download times

Gzip can be used on
JS
CSS
XML
JSON

Gzip should not be used on
Images
PDFs
Compressed data formats

CSS Sprites favicon

Badly optimized Thumbnails PNG can be compacted 50%, no quality loss OptiPNG

Test on slow connections Slow proxies for developers

Data served through a single domain Smart routing software Data closer to the end user – Less latency

Amazon CloudFront

Appropriate dates Cache far in the future Change file names on releases

Hash tag to compare between browser and server Gives more flexibility than last-modified-date Great on a single server setup

Typically unique to a server Disable if not being used!

Use options that are not unique per server

Firebug Firecookie Yslow Hammerhead http://stevesouders.com/hammerhead/

“ Knowledge rests not upon truth alone, but upon error also.” - Carl G. Jung

Caching for Cash - Part 4

by Helgi Þormar Þorbjörnsson

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