June 23, 2010

All Velocity conference 2010 Slides/Notes

Here are all the slides/PDFs which I’ve come across from the first 2 days at velocity, please let me know if I missed any.

 

    • Slides

    Speeding up 3rd party widgets using ASWIFT

    This is a summary of the talk by Arvind Jain, Michael Kleber from Google at velocityconf about how to write widgets using same domain iframe using document.write. Speed improvements of over 90% in loading widgets with this change.

    • Web is slow
      • Avg page load time 4.9s
      • 44 resources, 7 dns requests, 320kb
      • Lot of 3rd party widgets
        • digg/facebook/etc
    • Measurements of 3rd party widgets
      • Digg widget
        • 9 HTTP requests, 52 kB
        • scripts block the main page from downloading
        • stylesheets blocks the main page from rendering in IE
      • Adsense takes up  12.8% page load time
      • Analytics takes up < 5%   ( move to async widget )
      • Doubleclick takes up 11%
    • How to make Google AdSense “fast by default”
      • Goals / Challenges
        • Minimize blocking the publishers page
        • Show the ad right where the code is inserted
        • Must run in publishers Domain
      • Solution (ASWIFT) - Asynchronous Script Written into IFrame Tag
        • Make show_ads.js a tiny loader script
        • Loader creates a same-domain iframe (using document.write)
        • Loads the rest of the show_ads into the iframe by document.write() of a <script> tag
        • This loading of iframe is asynchronous.
      • Browser specific surprises
        • Problems with parallel downloads of same script in IE
        • Iframe creation inside <head> in Firefox has a problem
        • Requesting headers in Chrome was buggy
        • Forward-Back-Reload behavior is buggy (refetching instead of using cache)
        • document.domain vs friendly iframes

    Urs Holzle from google on “Speed Matters”

    From Urs’ talk at the velocity2010 conference [ More info : Google, datacenterknowledge ]

    • Average web page - 320kb, 44 resources, 7 dns lookups, doesn’t compress 3rd of its content
    • Aiming for 100ms page load times for chrome
    • Chrome: HTML5, V8 JS engine, DNS prefetching, VP8 codec, opensource, spurs competition
    • TCP improvements
      • Fast start (higher initial congestion window)
      • Quick loss recovery (lower retransmit timeouts)
      • Makes Google products 12% faster
      • No handshake delay (app payload in SYN packets)  [ Didn’t know this was possible !!! ]
    • DNS improvements
      • Propagate client IP in DNS requests (to allow servers to better map users to the closest servers)
    • SSL improvements
      • False start (reduce 1 round trip from handshake)
        • 10% faster (for Android implementation)
      • Snap start (zero round trip handshakes, resumes)
      • OCSP stapling (avoid inline roundtrips)
    • HTTP improvements (SPDY):
      • Header compression
      • Stream multiplexing and prioritization
      • Server push/hints
      • 25% faster
    • Test done
      • Download the same “top 25” pages via HTTP and SPDY, network simulates a 2Mbps DSL link, 0% packet loss - Number of packets dropped by 40%
      • On low bandwidth links, headers are surprisingly costly. Can add 1 second of latency.
    • Public DNS:
      • reduces recursive resolve time by continuously refreshing cache
      • Increases availability through adequate provisioning
    • Broadband pilot testing going on
      • Fix the “last mile” complaint
      • Huge increase of 100x
    • More developer tools by Google
      • Page speed, speed tracer, closure compiler, Auto spriter
    • More awareness about performance

    James Hamilton: Data center infrastructure innovation

    Summary from James’ keynote talk at Velocity 2010 James Hamilton

    • Pace of Innovation – Datacenter pace of innovation is increasing.  The high focus on infrastructure innovation is driving down the cost, increasing reliability and reducing resource consumption which ultimate drives down cost.
    • Where does the money go ?
      • 54% on servers, 8% on networking, 21% on power distribution, 13% on power, 5% on other infrastructure requirements
      • 34% costs related to power
      • Cost of power is trending up
    • Clouds efficiency – server utilization in our industry is around 10 to 15% range
      • Avoid holes in the infrastructure use
      • Break jobs into smaller chunks, queue them where ever possible
    • Power distribution – 11 to 12% lost in distribution
      • Rules to minimize power distribution losses
        • Oversell power – setup more servers than power available. 100% of servers never required in a regular datacenter.
        • Avoid voltage conversions
        • Increase efficiency of conversions
        • High voltage as close to load as possible
        • Size voltage regulators to load and use efficient parts
        • High voltage direct current a small potential gain
    • Mechanical Systems – One of the biggest saving is in cooling
      • What parts are involved ? - Cooling tower, heat exchanges, pumps, evaporators, compressors, condensers, pumps… and so on.
      • Efficiency of these systems and power required to get this done depends on the difference in the desired temperature and the current room temperature
      • Separate hot and cold isles… insulate them (don’t break the fire codes)
      • Increase the operating temperature of servers
        • Most are between 61 and 84
        • Telco standard is 104F (Game consoles are even higher)
    • Temperature
      • Limiting factors to high temp operation
        • Higher fan power trade-off
        • More semiconductor leakage current
        • Possible negative failure rate impact
      • Avoid direct expansion cooling entirely
        • Air side economization 
        • Higher data center temperature
        • Evaporative cooling
      • Requires filtration
        • Particulate and chemical pollution
    • Networking gear
      • Current networks are over-subscribed
        • Forces workload placement restrictions
        • Goal: all points in datacenter equidistant.
      • Mainframe model goes commodity
        • Competition at each layer rather than vertical integration
      • Openflow: open S/W platform
        • Distributed control plane to central control