I have noticed that my particular instance of Trac is not running quickly and has big lags. This is at the very onset of a project, so not much is in Trac (except for plugins and code loaded into SVN).
Setup Info: This is via a SELinux system hosted by WebFaction. It is behind Apache, and connections are over SSL. Currently the .htpasswd file is what I use to control access.
Are there any recommend ways to improve the performance of Trac?
It's hard to say without knowing more about your setup, but one easy win is to make sure that Trac is running in something like mod_python, which keeps the Python runtime in memory. Otherwise, every HTTP request will cause Python to run, import all the modules, and then finally handle the request. Using mod_python (or FastCGI, whichever you prefer) will eliminate that loading and skip straight to the good stuff.
Also, as your Trac database grows and you get more people using the site, you'll probably outgrow the default SQLite database. At that point, you should think about migrating the database to PostgreSQL or MySQL, because they'll be able to handle concurrent requests much faster.
We've had the best luck with FastCGI. Another critical factor was to only use https for authentication but use http for all other traffic -- I was really surprised how much that made a difference.
Serving the chrome files statically with and expires-header could help too. See the end of this page.
I have noticed that if
select disctinct name from wiki
takes more than 5 seconds (for example due to a million rows in this table - this is a true story (We had a script that filled it)), browsing wiki pages becomes very slow and takes over 2*t*n, where t is time of execution of the quoted query (>5s of course), and n is a number of tracwiki links present on the viewed page.
This is due to trac having a (hardcoded) 5s cache expire for this query. It is used by trac to tell what the colour should the link be. We re-hardcoded the value to 30s (We need that many pages, so every 30s someone has to wait 6-7s).
It may not be what caused Your problem, but it may be. Good luck on speeding up Your Trac instance.