HP PAK Performance Analysis Tools User's Guide

18 Chapter 2
Puma Concepts
How Puma Gathers Data
command-line mode, Puma either creates or overwrites
DataSet1.puma. Use the -dat option to create a data file with a
different name.
When invoked in graphical mode, Puma displays icons for the data files
that reside in the directory where it is executing, and that have the
filename extension .puma. You can load data files with other filename
extensions manually from within Puma.
To reduce the overhead cost of collecting data, Puma does not write data
immediately upon collecting it. Instead, Puma stores data in memory
and only writes to a data file when:
• you exit Puma
• you restart data collection
• you select some older data file for analysis
Sample Interval
The sample interval is the rate at which Puma takes data samples.
The sample interval refers to the amount of time that Puma allows the
target program to run before suspending it to record information.
The phrase samples per second refers to the number of samples gathered
for each second that the target program has been allowed to run. The
number of samples gathered by Puma per elapsed (real) second depends
upon the amount of overhead Puma incurs between each sample.
Overhead includes the time it takes to stop the target, record
information, update the graphical display, and restart the target.
By default, the sample interval is 100, which means that Puma gathers a
sample every 100 milliseconds of the target process execution time (at a
rate of 10 samples per second). This interval is under user control.