created: 20190316163428191
modified: 20190510133455372
tags: Features
title: Performance Instrumentation
type: text/vnd.tiddlywiki

The core has built-in performance instrumentation for the refresh cycle. See “Performance Instrumentation” on the “Settings” tab of control panel. The wiki will need to be reloaded before it takes effect.

With performance instrumentation switched on, there is additional timing information displayed the browser developer console each time a refresh cycle is triggered. For example:

```
performance: mainRender: 327.83ms 
performance: styleRefresh: 9.14ms 
performance: mainRefresh: 68.10ms 
```

The information above should be interpreted as follows:

* mainRender is the time taken for the initial display of the page template
* styleRefresh is the time taken to refresh the page stylesheet
* mainRender is the time taken to refresh the main page template

As an example, try switching between the sidebar tabs to compare how long they take to render.

More detailed information on filter execution timings is also available. With performance instrumentation enabled, type the following JavaScript command in the browser developer console:

```
$tw.perf.log()
```

A table is displayed with the following information:

* ''name'' - the string "Filter: " plus the text of the filter
* ''invocations'' - the number of invocations of the filter since startup
* ''totalTime'' - the total time in milliseconds spent evaluating this filter since startup
* ''percentTime'' - the percentage of the execution time of this filter against the total execution time of all filters
