= 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: [[TicketQuery(status=!closed,keywords=~performance,order=severity,format=table)]] == Performance Analysis === Load Testing Large loads can be simulated in the following ways: - using [http://jmeter.apache.org/ JMeter], see TracPerformance/LoadTestingWithJmeter - using [http://httpd.apache.org/docs/2.2/programs/ab.html ApacheBench] `ab`, see [./0.11.5#HowItimed]. ''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 }}} === Profiling Page load measurements can be collected by using profiling tools: - #7490 contains some profiling data. - Instructions about profiling Trac: [./0.11.5#Profilingissues]; 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() 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): {{{ #!python 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). === Genshi 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#Genshi], 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 
 instead of tables rows for rendering lines in the browser view. See #7055.

Let's not forget alternatives:
 - Proposals/Jinja
 - [http://kajiki.pythonisito.com Kajiki]
 - [http://groups.google.com/group/genshi/browse_thread/thread/4f66c2ca5302b807# Genshi Compiler]

=== gc.collect

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#gc.collect].
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.

=== Miscellaneous

 - 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:
 - better use of caching headers:
   - add `Cache-Control: public`
   - add `Expires: `''(future)'', `Cache-Control: max-age` together with URL fingerprinting, #9936
   - fix `Vary:` header #6367
   - verify we call `req.check_modified()` as appropriate #4022
   - reference: http://code.google.com/speed/page-speed/docs/caching.html
 - request handler shortcut? #9938
 - htdocs_location => chrome_location #9683
 - make it possible to use CDNs for jquery #10244 (and later jqueryui #10245)
 - use http://headjs.com/ for loading scripts in parallel?

Optimizing browser rendering by improving the CSS selectors:
 - avoid ''Rules with a tag selector as the key''
 - avoid ''Rules with overly qualified selectors''
 - ''Remove redundant qualifiers''
 - ''Don't use @import''
 - reference: http://code.google.com/speed/page-speed/docs/rendering.html