Jonathan Kamens (jik(a)kamens.us) said:
I restarted Firefox many times. I restarted gnome-shell. I restarted
my machine. Nothing helped. Performance was poor immediately after
the restart. There was no perceivable degradation over time -- it
was extremely poor right from when it started up and stayed that
way.
In my experience, extremely slow FF performance is usually due to
writing out either the assorted sqlite data files in the profile
directory, or the big javascript pile that is the session storage.
Not sure why move/replace would fix that, though.
Bill