Statistics Caveats (Oracle Waveset 8.1.1 System Administrator's Guide)

Oracle Waveset 8.1.1 System Administrator's Guide

Statistics Caveats

The following sections contain information to consider when you evaluate results provided by the Profiler:

Self Time Statistics: To compute a root node’s Self Time statistic, the Profiler subtracts the times of all children nodes from the root node’s total time. Consequently, an uninstrumented child node’s time is reflected in the root node’s self time. If a root node has a significant self time, you should certainly investigate why. You might not have the proper methods instrumented and so you are looking in the wrong place. For example, assume method A calls method B.

Method A takes a total time of 10 seconds (where total time includes the call to B) and the call to B takes a total time of 10 seconds.

If both A and B are instrumented, the call stack reflects that information. You will see that A has a self-time of 0 seconds and that B has a self-time of 10 seconds (where 10 seconds was actually spent in B). If, however, B is not instrumented, you only see that the call to A takes 10 seconds and that A’s self-time is 10 seconds. Consequently, you might assume the problem lies directly in A rather than in B.

In particular, you might notice large self times on JSPs during their initial compile. If you reset the collected results and then re-display the page, the self time value will be much less.

Constructor Calls: Because there are limitations in the Java instrumentation strategy, initial calls to this() or super() will appear as a sibling to the constructor call, rather than as a child. See the following example:

class A
{
   public A()
   {
      this(0);
   }
   public A(int i)
   {
   }
}

and:

class B
{
   public static void test()
   {
      new A();
   }
}
The call tree will look like this:
B.test()
   -A.<init>(int)
   -A.<init>()
Rather than this:
B.test()
   -A.<init>()
      -A.<init>(int)

Daemon Threads: Do not be misled by the seemingly large amount of time spent in a number of Waveset’s daemon threads, such as ReconTask.WorkerThread.run() or TaskThread.WorkerThread.run(). Most of this time is spent sleeping, while waiting for events. You must explore these traces to see how much time is actually spent when they are processing an event.