A user contacted me complaining of frequent 2- to 4-second freezes when running Firefox with ~20 open tabs, with several web development add-ons installed including YSlow 3.1.2 and Firebug 1.10b4. I asked him to try Gecko Profiler, and he sent back the following profile from a time when Firefox was acting slow: http://people.mozilla.com/~bgirard/cleopatra/?report=869f03a73dd857485879e7c3b2f196e2f612cc48 About half the time in the profile is spent in YSlow code, with the majority of that in an anonymous function at yslow-ff-pref.js:66.
I reported this issue to the YSlow project, with some additional details from inspecting the YSlow 3.1.2 source code: https://github.com/marcelduran/yslow/issues/49
Thanks for the catch, I just removed the unused getPrefList block and increased startup timeout as an attempt to fix this issue. Please let me know if this really fix the reported issue.
Just submitted a new Firefox Addon: YSlow 3.1.3 which is pending review: https://addons.mozilla.org/en-US/firefox/addon/yslow/versions/?page=1#version-3.1.3
And 3.1.3 is now fully reviewed, thanks reviewers!
Thanks! Resolving this as fixed for now, though I can't verify it myself because I was not able to reproduce the problem. I asked the original reporter to verify the fix, and I'll update this bug if I hear back.