Bugzilla::local_timezone calls DateTime::TimeZone->new(name => 'local') which is very slow. It takes 0.2 second on my machine, for each page call. The local timezone won't change while a process is running, and so there is no need for this timezone object to be rebuilt again and again. It should be stored in process_cache instead of request_cache.
Created attachment 701110 [details] [diff] [review] patch, v1
Comment on attachment 701110 [details] [diff] [review] patch, v1 r=glob
Committing to: bzr+ssh://firstname.lastname@example.org/bugzilla/trunk/ modified Bugzilla.pm Committed revision 8556. Committing to: bzr+ssh://email@example.com/bugzilla/4.4/ modified Bugzilla.pm Committed revision 8504.