Edgewall Software

Version 16 (modified by Ryan J Ollos, 7 years ago) ( diff )

Pygments moved their issue tracking to BitBucket.

Trac and Performance

With Trac 0.11, the ClearSilver template engine was replaced with the Genshi template engine, but with its increased flexibility, Trac also became slower and memory hungry. As memory usage seems now mostly OK (#6614), there are still many concerns over Trac's performance.

However, apart from Genshi, there are several other factors to be taken into account when analyzing performance:

  • the increased usage of plugins, each of them can add to the load in subtle ways
  • the new security model of TracFineGrainedPermissions
  • the conditions in which Trac is run (web front-end)
  • the specific configuration settings of Trac
  • various bugs that might be triggered by any of the above!

This page collects Trac performance issues, solutions and troubleshooting.

Check your installation

If Trac is not installed correctly, performance will suffer. The most obvious mistake is installing Trac as a CGI script. Even for testing, there are better alternatives, see tracd.

The second main installation mistake relative to performance would be to serve static resources through Trac. For best performance, Trac pages are better served by a web server, see TracCgi#MappingStaticResources.

(Note: we should probably move the mapping static resources section to another page, e.g. TracModWSGI)

Other points worth checking:

  • if using mod_python, only use latest version (3.3.1); prefer mod_wsgi (≥ 2.4), ie daemon mode
  • running Trac under the QEMU virtualizer is slow (ticket:7490#comment:42)
  • in Apache, there's a possible issue when using mod_deflate (#8534, googlegroups:trac-users:ab070d251f5a0d11); on the other hand, some people have good results with mod_deflate and advise using it (TracDev/Performance/0.11.5)
  • some 3rd party packages, such as Pygments, could also be responsible for heavy CPU loads; specifically, Pygments 1.0's scala mode, see Jespern's blog entry (see also #392).
  • ensure an image has been configured as the trac logo in the top left. The default install from Ubuntu 10.04 for example does not include a default logo and this makes pages slow to load.

Check your configuration

Several settings enhance Trac in one way or the other, but have a performance cost, which in some cases can be large.


  • default_daysback set to a high value might introduce quite some load, depending on the activity. Pick an appropriate value for your site.
  • the default max_daysback can be inappropriate, eg allowing 90 days for a site with lots of activity might be too much. Don't hesitate to reduce it, especially now that we have paging
  • any setting other than changeset_show_files = 0 can be really expensive, depending on the quantity of changesets to process


  • use of restrict_owner = true can be slow on some installations (see #4245, #8034, #8212 …)

Check your trac.log

Search for the following:

  • INFO messages: Reloading environment due to configuration change
    If you find lots of such lines, or even worse, if they appear systematically, then chances are that you're using a plugin which does systematic updates to the configuration file trac.ini, and this will in turn trigger a full environment reload at the next request. That can slow down the performance a lot, to the level of TracCgi. See ticket:7490#comment:102 and follow-up.
  • INFO messages: rev [321] != cached rev [123] (other revision numbers for you, of course)
    If you find such lines and the cached rev value doesn't change, this corresponds to a repository resync failure, which results in a resync attempt for every request (see ticket:7490#comment:36); often as a result of the "prohibited" MySQL/MyISAM combination (#8067).
  • WARNING message: Slow mail submission
    A mis-configured or simply slow mail server make Trac appear very slow (#3220 and numerous others).


  • There was a bug up to 0.11.4 which could cause 100% CPU usage once in a while on some platforms (#7785, thought to be fixed in 0.11.5, but re-opened since).
  • Some plugins seem to have a high impact on the performance, see TracDev/Performance/0.11.5.

Profiling a Trac request

I've written a blog post on how I do basic profiling for Trac. It includes a simple script that I use to check single requests. Read it @ my blog.

— osimons

See also: TracDev/Performance

Note: See TracWiki for help on using the wiki.