Over the weekend I spent some serious time with my computer running a bunch of tests with standalone talos in 11 different situations. First, a disclaimer: these tests were only designed to give some insight on the areas we should focus on for the goal. Each of these tests was reproduced at least once before I moved onto the next one in order to make sure the numbers were stable.
- Clean profile. This is just the standard profile that we normally run Ts with on tinderbox. This is basically used a baseline for best possible performance.
- Dirty profile. This is actually my daily profile, with eight tabs that will open through session restore during startup. Because of how talos works, these tabs don’t all have to load for the number to be generated. Even so, you’ll notice a substantial slowdown. Sadly, I fear I modified the profile I was using in a bad way because I can no longer reproduce the numbers I got (but the numbers recorded were reproduced four times before I moved on to the rest of the tests initially).
- Bookmarks toolbar disabled. This is a variation on the dirty profile test that just disables the bookmarks toolbar.
- No places. This is a variation on the dirty profile test that removes places files from the profile.
sessionstore.js. This is a variation on the dirty profile test that removes
sessionstore.jsfrom the profile. This has the side effect of also not making the eight tabs load at startup.
- No urlclassifier. This is a variation on the dirty profile test that removes the urlclassifier related files from the profile.
cookies.sqlite. This is a variation on the dirty profile test that removes
cookies.sqlitefrom the profile.
- No extensions. This is a variation on the dirty profile test that removes all add-on manager bits in the profile.
formhistory.sqlite. This is a variation on the dirty profile test that removes
formhistory.sqlitefrom the profile.
downloads.sqlite. This is a variation on the dirty profile test that removes
downloads.sqlitefrom the profile.
content-prefs.sqlite. This is a variation on the ditry profile test that removes
content-prefs.sqlitefrom the profile.
I’m going to let some graphs do the talking here. The first shows the raw test run data (which isn’t terribly interesting). The second compares the reported startup time for each test. You will probably want to click to zoom in.
It looks like the best wins that we can get are related to fixing session restore to not scale linearly with the number of tabs it is restoring, and reduce the startup time costs of loading places files and
cookies.sqlite. It should be noted that this test was not measuring the load time for each tab, so something like BarTab would not help in this case. The other good news is that we already have work underway to make cookies.sqlite load time not hurt us so much during startup.