Bug 594121 adds code to nice the child process. This seems to regress Txul (Twinopen) by ~500ms. It might also regress Ts, but it was conflated with the omnijar change (bug 608742), which also regressed Ts a little. Graphs: http://bit.ly/9D1bAW Tbox: http://tinderbox.mozilla.org/showbuilds.cgi?tree=Mobile&maxdate=1288981957&hours=24&legend=0 Changeset: http://hg.mozilla.org/mozilla-central/rev/6edccbb39c1b Omnijar changeset for reference: http://hg.mozilla.org/mobile-browser/rev/a6d28a17b56c Bug 608742 has been backed out and the Txul regression is unchanged. Ts improved slightly, but not significantly.