HPjmeter 4.3 User's Guide

Monitor Threads and/or Locks Menu
Thread Histogram
Displays thread states over time. Thread data arrives in time slices. For each time slice, color-coded
bars represent the percentage of time the thread spent in each state. The reported states are:
Waiting The thread has been suspended using Object.wait() method.
Lock Contention The thread is delayed while attempting to enter a Java monitor that is
already acquired by another thread.
Running All remaining cases.
Guidelines
• Large amounts of red in Thread Histogram indicate heavy lock contention, which is usually a
possible problem. On the other hand, large amounts of green indicate a potential processing
capacity for the involved threads.
• When there is no load, the state for the threads doing the work on behalf of transactions
should be waiting, and marked by the green color.
• Threads terminating normally, or because of uncaught exceptions, appear as a discontinued
row.
• Multiple short-lived threads appear as apparently blank rows in the display. At the same time
the number of displayed threads, shown at the bottom of the display, is large.
• Lock Contention appears as red in the display.
• Deadlocked threads appear as two or more threads spending all their time in lock contention,
red, starting from a given time. This point in time identifies the deadlock occurrence.
Details
For each time slice, represented by a small portion of the X-axis, the display along the Y-axis shows
the percentage of the time slice that the thread spent in each state. It represents a stacked bar
graph for the time slice.
Figure 47 Monitoring Metric: Thread Histogram
152 Using Visualizer Functions