Revision as of 18:52, 28 September 2010

When you're trying to figure out why your application is slow, or when you're performance tuning to improve the performance, you can use the Profile tab in /resin-admin to quickly find the methods that are taking the most time.

The Profile allows dynamic measurement of the application's CPU usage as measured by taking periodic thread dumps. Since the overhead of the profiling is relatively low, you can even use it in a live server to troubleshoot performance problems.

In general, you want to focus on the top 10 or 20 methods because a method that only takes 0.1% of the total time generally isn't worth performance work.

The profile is organized as a list of methods with columns summarizing the time taken by the method.

Profile Columns

 % time

The time taken by the method as a percentage of the profile time. Because multiple threads can be executing the same method simultaneously, this number can be larger than 100%.

time self

The time in seconds taken by this method. Because the time includes all threads, it can be larger than the total profile time.

 % sum

Measures the percentage of the total time taken by all the members in the group.

Example