TCP and the Lower Bound of web performance

One of the less discussed, but highly informative and very thought provoking talk during Velocity 2010 was the one about TCP, latency, window sizes and its relation to web performance. The slides to this talk by “John Rauser” can be found here. And thanks to Mike Bailey, there is a video recording as well.

Follow the slides as you watch the video to understand the talk.

TCP and the Lower Bound of Web Performance – John Rauser from Goodfordogs on Vimeo.

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

    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