Firefox/Projects/Startup Time Improvements

Overview

Sprint lead: Dietrich Ayala
Sprinters: Ryan Flint, Drew Willcoxon, David Dahl
Concurrent work: Vlad Vukićević, Taras Glek

Description: Investigate areas for improving startup time of the Mozilla platform, find & fix issues that help Fennec and WinCE.

Bugs that affect startup are identified by "[ts]" in the whiteboard field.

• ts bugs.

Instrumentation

Create an easily accessible timeline of the startup path (David, Vlad)

• Status: in progress
• Usage: steps here
• Results
  • bug 480735 instrumentation
  • bug 503605 visualization
  • Example output: Simile timeline
  • Example output: raw log

Mine the Ts DTrace viz/logs (Drew)

• Status: complete, moved on to filesystem operations below
• Results
  • It's my conclusion that (cold) startup is heavily I/O-bound. Something like 90% of cold startup time is spent in page faults and other I/O syscalls, especially read, getattrlist, and stat. And the majority of time spent after Firefox actually gets up and running is in XBL and CSS. Any improvements that ignore these observations will therefore be marginal IMO.
• Bugs
  • bug 504858 - Investigate delaying initialization of bookmarks toolbar
  • bug 504872 - Investigate further delaying initialization of the search bar
  • I think these two bugs aren't worth pursuing. As Gavin comments in them, the latency I noticed is due to unavoidable things like XBL attachment and flushing layout. Moreover, they contribute very, very little to startup time.

Log and mine filesystem operations during startup (Ryan, Drew)

• Status: in progress
• Todo
  • maybe write a new dtrace script for targeting offenders
• Results
  • checking out Xperf and others for Windows work
    • investigating dtrace timing/FS cache issues on OS X
      • Instruments appears to have the same issues
    • Simple JS file exec script has yielded some results
  • Drew's notes
  • Joel's notes
• References
  • Josh Aas's post
  • Taras' post on using GDB for logging
  • Firefox/Projects/Startup_Time_Improvements/IO_Scratchpad

Current Activity

Find dead code with JSHydra (David Dahl)

• Status: in progress
• Todo
• Results
• Bugs
  • bug 506128 - run jshydra to find js functions that have no callers

Testing

Dirty profile testing (Alice, David Dahl, Dietrich)

• Status: partially complete
• Todo
  • Create various scenarios to measure
    • sessions, downloads, cookies, urlclassifier data
  • Fix date updater for med/large profiles
  • Roll-up reporting of results
• Results
  • Builds marked "dirty" on the tree

Cold Startup Measurement (Alice, Drew)

• Status: in progress
• Todo
  • Talos patches for head/tail script support
  • Talos head/tail scripts for cold startup for all platforms
    • disable fastload, OS-specific calls
  • deploy to test tree
  • deploy to mozilla-central
• Done
  • determine simulated cold startup methods for all platforms
• Results

JSHydra continuous testing

• Status: not started
• Todo
  • Feasibility analysis: need to find out if even possible
  • Determine test scenarios
    • ending semicolon bug (XXX)
    • dead code finder

Needs Action

Notes, other ideas to develop further, bugs to file, etc.

TODO:

• enumerate findings, convert to best practices recommendation
• user-runnable Ts script
  • paste into js console
  • restarts browser, passing last known time
  • loads data URI that reads startup time and prints it out
  • record startup timestamp as a pref?

Bugs:

• FILEME - minification packaging step
• bug 507101 - component combining packaging step
• bug 509755 - modules into jar file packaging step
• FILEME - micro-benchmark tests
  • see also the mochitests i wrote for this (find the places bug for this)
• FILEME - dirty test (or micro?): need test for opening the 80th tab for example
• FILEME - tracing/trace-ability reporting
  • traceviz (bug 497999)
• FILEME - other dirty profiles
  • sessions, downloads, urlclassifier data, post-crash session
• sql query count measurement (find my bug for this)

Needs investigation:

• .order files (webkit)
• string pool for jsxpcom

References

Meta bugs

• bug 459117 Fennec performance meta bug
• bug 447581 Startup meta bug
• bug 479078 Startup research meta bug
• bug 7251 very old startup meta bug

• Vlad's blog posts
  • Vlad's June posting on startup work
  • Vlad's July posts: 1 2 3 4 5

• zpao's JS treemap visualizations
  • newer
  • older

• Taras' Fennec Startup Work
  • bug 459117 "make fennec faster", mostly startup bugs
  • startup log
  • bug 470116 various timing scripts

• Performance:Home_Page

Tips, Tools

• Flushing Windows' disk cache
• Flushing Mac OS X's disk cache
• Firefox/Projects/Startup_Time_Improvements_Notes: Vlad's emails about cold startup, including Linux (maybe move this info to this page)
• DTrace
  • nuts and bolts how-to for getting dtrace running with mozilla
  • project overview of integrating dtrace with mozilla
  • dtrace community page, lots of links
  • dtrace homepage? not as useful as previous link
  • intro from dtrace guidebook, really useful but not mozilla/js-specific
  • brief descriptions of the javascript* probes
  • David Mandelin's notes on tracing C++ code

Fastload

• why does js_Execute take so long for fastloaded components?
• what is fastload?
• fastload pref docs

Measuring Ts

• startup-unix.pl in mozilla/tools/performance/startup
  • edit it to use this HTML in place of startup-test.html:

<html>
<body onload="
  var now = (new Date()).getTime();  
  var begin = document.location.search.split('=')[1]; // ?begin=nnnnn
  dump((now - begin) + '\n');
  window.close();
">
</body>
</html>

• • set dom.allow_scripts_to_close_windows and browser.dom.window.dump.enabled to true in your testing profile
  • run it in a loop to collect more stable results:

#!/bin/bash
cd ~/moz/trunk/mozilla/tools/performance/startup
for ((i=0; i < 5; i++)) do perl startup-unix.pl ~/moz/trunk/build-dbg/dist/MinefieldDebug.app/Contents/MacOS/firefox-bin -P startup >> results.txt; done;