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A Faster FasterFox?

A Faster FasterFox?. David Backeberg and Remo Mueller. Firefox “Out of the Box”. Memory cache set proportional to system ram Disk cache set to default value (76,800 KiB) “Prefetching” enabled: network.prefetch-next set to true. Browser content caching.

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A Faster FasterFox?

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  1. A Faster FasterFox? David Backeberg and Remo Mueller

  2. Firefox “Out of the Box” • Memory cache set proportional to system ram • Disk cache set to default value (76,800 KiB) • “Prefetching” enabled: network.prefetch-next set to true

  3. Browser content caching • HTTP/1.1 200 OK Date: Fri, 30 Oct 1998 13:19:41 GMT Server: Apache/1.3.3 (Unix) Cache-Control: max-age=3600, must-revalidate Expires: Fri, 30 Oct 1998 14:19:41 GMT Last-Modified: Mon, 29 Jun 1998 02:28:12 GMT Content-Length: 1040 Content-Type: text/html • HTML also supports tags involving caching. Not necessarily honored by browsers. • <META HTTP-EQUIV="CACHE-CONTROL" CONTENT="NO-CACHE">

  4. Everyone wins • Browser doesn’t have to grab something it already has • Server / client don’t waste bandwidth on redundant content • User thinks website is “faster”, more likely to make return visits to website

  5. Firefox Extensions (.xpi) • Third-party applications that use Firefox library functions to accomplish some task • Examples • Forecastfox (weather info on toolbar) • Flashgot (replaces Firefox download ability with richer functions)

  6. Firefox prefetching • Firefox extends HTML link tag • <link rel="prefetch" href="mozspecific.css"> <link rel="next" href="2.html"> • This method isn’t forbidden, it merely creates a new kind of “relation”, permitted by HTTP 1.1 • If “rel” is “prefetch” or “next”, Firefox will prefetch the page(s)

  7. Firefox Prefetching • Prefetching only uses “idle” bandwidth • We put “idle” in quotes because the browser can’t tell what else is going on with network activity in other system applications or daemons • Once all tabs or pages are loaded, Mozilla will grab explicitly tagged content

  8. Firefox Prefetching • Prefetched content ends up in disk-cache. • Prefetching makes the cache more relevant, and “fresher” than it would be without prefetching • User has illusion of faster browsing

  9. Firefox settings • Settings can be viewed and changed with about:config • These settings can also be changed with prefs.js in user’s directory • Cache contents and settings can be viewed with about:cache

  10. Firefox internals • Individual functions (library calls) within Firefox can be put into debug mode • Under linux:$export NSPR_LOG_MODULES=nsHttp:5,nsSocketTransport:5,nsHostResolver:5, nsPrefetch:5$export NSPR_LOG_FILE=/home/dave/eecs428/fasterfox/http.log$firefox • In this manner we could get a log of whether prefetching was working • Examined cache using about:cache • Recorded page load times

  11. Fasterfox • An .xpi-based extension of Firefox • Uses Firefox library calls to provide richer prefetching and caching abilities • Also “tweaks” page rendering techniques to display content faster • Tunable “aggressiveness”

  12. Fasterfox Settings • Some settings are just user-friendly GUIs for changing settings buried in about:config

  13. Fasterfox Settings • Other settings are genuine extensions of the way Firefox downloads pages

  14. Enhanced Prefetching • Doesn’t restrict prefetching to rel=next, rel=prefetch links • Index up to 100 links on a page, prefetch all of those, as long as they look like static content • Try not to prefetch a “logout” or “empty my shopping cart” button

  15. Enhanced Prefetching • Very good odds of user clicking a cached page, and that cached version being up-to-date • Also good odds of cache containing data that won’t be viewed by user • Arguably, for a site the user visits heavily, this could still mean everybody wins

  16. How We've Modified Fasterfox: • Fasterfox now keeps track of how long it took to visit each page. After running a test series, we can gather all the information and perform an analysis of it. • We also changed the content that is grabbed in Fasterfox

  17. Timings screenshot

  18. How to Enhance Fasterfox • Prioritized Prefetching (Fasterfox currently uses a fifo queue, ordered by the link’s location on a page) • Global System view of bandwidth; prefetch only when system idle? • Gentler prefetching mechanism? Prefetching uses ordinary HTTP GET. Perhaps a PREGET? • User Customization • Different user types • User selects, or artificial intelligence to figure out what type the user is. • Cache hit rate percentage (prove that prefetching is really making the cache more relevant)

  19. References: • Firefox Link Prefetching FAQhttp://www.mozilla.org/projects/netlib/Link_Prefetching_FAQ.html • Fasterfox source codehttp://fasterfox.mozdev.org/ • Mozilla HTTP Debugging guidehttp://www.mozilla.org/projects/netlib/http/http-debugging.html • Assertion: Prefetching With GET Is Not Good, Brian Davison. Proceedings of the Sixth International Web Content Caching and Content Distribution Workshop (WCW'01), Boston, June 20-22, 2001, pages 203-215. Available online: http://www.cse.lehigh.edu/~brian/pubs/2001/wcw/wcw01.pdf

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