HPjmeter 4.3 User's Guide

Related Topics
• Thread Deadlock Alert (page 133)
• Thread Histogram (page 152)
Identifying Excessive Thread Creation
Use the Thread Histogram to identify excessive thread creation.
The Thread Histogram shows the number of threads existing in the observed period of time. By
selecting the smallest time interval, one minute, you can see an estimate of the number of
simultaneously active threads. Most operating systems have a limited capacity for the number of
threads a single process may create. Exceeding this capacity may cause a crash. Although HPjmeter
cannot indicate whether or not this will happen, the intensity of the new thread creation may suggest
deeper analysis is needed in this area.
Adjusting kernel parameters may increase the threads per process limit.
Sometimes an application may exhibit threads leak, when the number of dynamically created
threads is unconstrained and grows all the time. Tuning kernel parameters is unlikely to help in
this situation.
Related Topics
• Thread Histogram (page 152)
Identifying Excessive Method Compilation
HPjmeter allows you to enable an alert that identifies excessive method compilations. You can then
use the Method Compilation Count display to view the specific method or methods that caused the
alert.
Symptoms of excessive method compilation include poor application response because the JVM
is spending time re-compiling methods.
The Method Compilation Count display shows the methods that have been compiled, sorted by
number of compilations.
Figure 5 Example Metric: Method Compilation Count
Excessive method compilation is rare, especially with newer releases of JVM. Sometimes, due to
a defect in the JVM, a particular method can get repeatedly compiled, and de-optimized. This
means that the execution of this method oscillates between interpreter and compiled code. However,
56 Monitoring Applications