Edgewall Software

Improving Trac Performance

On TracPerformance some ideas for improving the performance of a Trac install have been discussed, this page collects some suggestions for performance meansurement and implementation ideas. Here's a list of the tickets tagged with the performance keyword:

Ticket Summary Status Keywords Owner Type Severity
#10606 GitPlugin: Improve performance new performance enhancement critical
#4245 [PATCH] Tickets are slow with large amount of users and permissions new patch performance slow restrict_owner get_users_with_permission defect major
#6986 MySQL schema changes for performance new performance mysql database patch enhancement major
#8813 next_rev is slow, particularly in the direct-svnfs case new slow performance newcache svn defect major
#10267 Version controls diffs of large text files kill the system new diff performance genshi defect major
#11185 improve speed of TicketQuery for format=table assigned performance genshi jinja2 javascript Christian Boos enhancement major
#1216 wiki pages caching new objectstore performance enhancement normal
#2636 browsing a directory with many files takes a long time new performance enhancement normal
#2827 Preview attachments in main ticket (or wiki) window new thumbail image attachment performance enhancement normal
#5499 performance issues when viewing larger files new blame performance defect normal
#6128 [Patch] Pagination for the Timeline new patch pagination performance enhancement normal
#6638 Allow file exclusions in diffs new bitesized performance enhancement normal
#6807 Option to skip revisions with lots of added files new performance enhancement normal
#7055 Add "toggle line numbers" JavaScript to source browser new javascript performance patch enhancement normal
#7739 trac & memcached new memcached performance enhancement normal
#7785 Trac slow / unreachable objects / database locked new performance database locked svn apr_terminate defect normal
#8058 Smarter db connection pool new performance, schema, postgresql enhancement normal
#8509 [PATCH] use precompiled regex for match_request new patch performance defect normal
#9938 Improve on static resources new performance enhancement normal
#10672 Automatically minify Javascript and CSS new javascript css performance enhancement normal
#11024 Losslessly compress images new performance enhancement normal
#11206 Reduce join in query process new mysql, performance enhancement normal
#12745 Changeset view with single revision which has many files is so slow new git performance enhancement normal
#12967 Reduce joins and subqueries in query module when many custom fields are used new join subquery performance enhancement normal
#8639 "View latest revision" links to non-existent (404) page new newcache performance defect minor
#9172 Trac diff highlighting start and end points new performance diff enhancement minor
#11826 Optimize ticket.query.execute new performance enhancement minor

Performance Analysis

Load Testing

Large loads can be simulated in the following ways:

For timing template generation, you can use ApacheBench and toss out "warmup" requests, sometimes testing with keep alive (getting slightly better req/s)

ab [-k] -c 1 -n 10 url


Page load measurements can be collected by using profiling tools:

  • #7490 contains some profiling data.
  • Instructions about profiling Trac: 0.11.5; see also #8507 which contains scripts by Shane Caraveo.
  • Some interesting profiling data from ticket:7490#comment:106, typical of a request triggering an environment reload. Edited to make it more readable:
             935179 function calls (910454 primitive calls) in 6.699 CPU seconds
       Ordered by: cumulative time
       ncalls  tottime  percall  cumtime  percall filename:lineno(function)
            1    0.000    0.000    6.699    6.699 ...trac/web/trac_profile.py:155(inspected)
            1    0.000    0.000    6.699    6.699 ...trac/web/wsgi.py:90(run)
            1    0.000    0.000    6.699    6.699 ...trac/web/main.py:314(dispatch_request)
            1    0.000    0.000    4.782    4.782 ...trac/web/main.py:432(_dispatch_request)
            1    0.000    0.000    4.782    4.782 ...trac/web/main.py:139(dispatch)
        43/41    0.003    0.000    2.894    0.071 ...trac/core.py:65(extensions)
      396/382    0.006    0.000    2.891    0.008 ...trac/core.py:194(__getitem__)
          105    0.157    0.001    2.786    0.027 ...trac/env.py:222(is_component_enabled)
            1    0.000    0.000    2.290    2.290 ...trac/web/chrome.py:706(render_template)
          2/1    0.000    0.000    1.867    1.867 ...trac/env.py:546(open_environment)
          6/2    0.001    0.000    1.733    0.867 ...genshi/template/loader.py:134(load)
          4/2    0.000    0.000    1.732    0.866 ...genshi/template/loader.py:242(_instantiate)
          4/2    0.001    0.000    1.732    0.866 ...genshi/template/base.py:345(__init__)
            1    0.000    0.000    1.476    1.476 ...trac/web/chrome.py:689(load_template)
        11699    0.098    0.000    1.423    0.000 ...trac/config.py:394(options)
            1    0.000    0.000    1.390    1.390 ...trac/env.py:175(__init__)
          189    0.007    0.000    1.349    0.007 ...genshi/template/eval.py:63(__init__)
            1    0.001    0.001    1.316    1.316 ...trac/loader.py:101(load_components)
            1    0.004    0.004    1.312    1.312 ...trac/loader.py:38(_load_eggs)
        11722    0.249    0.000    1.141    0.000 ...trac/config.py:296(get)
          382    0.163    0.000    1.102    0.003 {method 'sort' of 'list' objects}
          189    0.012    0.000    1.010    0.005 ...genshi/template/eval.py:423(_compile)
       806/67    0.010    0.000    1.006    0.015 ...genshi/template/base.py:412(_prepare)
            4    0.025    0.006    1.004    0.251 ...genshi/template/markup.py:72(_parse)
            1    0.000    0.000    0.995    0.995 ...trac/ticket/report.py:81(process_request)
           67    0.001    0.000    0.988    0.015 build/bdist.freebsd-6.1-RELEASE-i386/egg/pkg_resources.py:1911(load)
        63000    0.572    0.000    0.936    0.000 ...trac/env.py:236(<lambda>)
     2748/830    0.013    0.000    0.793    0.001 ...genshi/core.py:264(_ensure)
          940    0.020    0.000    0.762    0.001 ...genshi/template/interpolation.py:39(interpolate)
           99    0.001    0.000    0.705    0.007 ...genshi/template/directives.py:69 (attach)
            1    0.000    0.000    0.674    0.674 ...genshi/core.py:152(render)
            1    0.002    0.002    0.674    0.674 ...genshi/output.py:33(encode)
          231    0.004    0.000    0.667    0.003 ...genshi/output.py:302(__call__)
          234    0.001    0.000    0.662    0.003 ...genshi/output.py:751(__call__)
    • trac corresponds to Trac-0.11.5rc2-py2.5.egg and genshi to Genshi-0.5.1-py2.5-freebsd-6.1-RELEASE-i386.egg
    • Environment.is_component_enabled is unexpectedly slow
      • as Shane found out, config is really taking more time than expected. Only 0.1ms per call to get/options, but as this happens 11000 times, it is 1.1s.
      • also slow as a result of the following (line 236):
        rules.sort(lambda a, b: -cmp(len(a[0]), len(b[0])))
        There is some potential for caching rules here.
      • The problem should be fixed by r8644:8645, but this is to be confirmed by performing the profiling.

Improvement Opportunities

Web front-end

r8215 introduced HTTP1.1 support for tracd, but at the cost of making the Content-Length header mandatory. We should have added chunked-encoding support at the same time. Now that we have it (via #717), we could revert to streaming some of the responses (see ticket:717#comment:48).


The impact of Genshi is especially important for requests generating a big amount of data, like the changeset view or the file browser view, especially when compared to ClearSilver.

From 0.11.5, we can get the following ideas:

  • revert to out.write(_encode(u''.join(list(iterator)))) instead of using the StringIO; that was a change done during #6614, but we could have a favor_speed_over_memory setting
  • avoid the whitespace filter, same setting

Additionally, there's the idea to increase the size of the template cache for Genshi (#7842), also something that could be done if a favor_speed_over_memory configuration is active.

We could also gain some speed by not passing all the content through all the filters, but pre-render some parts in a faster way, then wrap them in Markup objects. That would make them opaque to the filters, but that would be most of the time OK, or the plugins that really need that could somehow selectively turn this optimization off. See #5499 (browser) and #7975 (changeset).

Also, the generated XHTML itself could certainly be improved: for example, using <pre> instead of tables rows for rendering lines in the browser view. See #7055.

Let's not forget alternatives:


According to Shane's analysis, the systematic gc.collect() call after every request is one of the most critical performance killers for the average request: 0.11.5. See proposed implementation of a secondary thread taking care of this: #8507.

Database level optimizations

  • #4425 - report of all unwritten pages
  • Some MySQL specific changes have been suggested, see #6986.
  • #6654 - pad revision numbers with leading zeroes

Also, we should also simply fix the current behavior when it's known to be problematic:

  • timeout when trying to get a db connection (happens again on t.e.o, could be related to #8443)
  • prefer short-lived transactions as much as possible (#3446). We should fetch all data in memory instead of iterating over cursors and doing some work while iterating. This is a memory vs. speed (and concurrency) trade-off.

On the topic of transactions, we should probably use the transaction idea from the WikiRename branch, as refined by rblank on Trac-dev (googlegroups:trac-dev:21d21ad9866fc12b). This would help to visualize the span of write transactions in the code and better handle query failures (#8379).

Permission checking

The whole TracFineGrainedPermissions was not designed with performance in mind and this shows in several places, like the ad-hoc additions of various caches in source:trunk/trac/perm.py.

Some places are still up for optimization, in particular the AuthzPolicy, which graduated from sample plugin to optional component. See ticket:9348#comment:6 for hints about what could be done.


  • Some more modules could use paginated results (#6128 - timeline, #6101 - browser) or on-demand display (#515 - changeset view), or… no display at all (#5170)
  • There was once the suspicion that DEBUG logging level could significantly impact performance. We need some numbers on this.

"Page speed" improvements

Improve static resource delivery:

Optimizing browser rendering by improving the CSS selectors:

Last modified 3 years ago Last modified on Feb 6, 2015, 8:57:04 AM
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