Use these tips to make IBM® Rational® Performance Tester run
faster and more efficiently. These tips do not apply to IBM Rational Service Tester for SOA Quality.
The following suggestions can help you to get the best performance
from Rational Performance Tester:
- Number of computers. Have at least two computers for a
test. The user interface consumes significant resources; therefore
play back a test or schedule on a computer (agent) that is separate
from the computer that is running the workbench (UI).
- Number of virtual users at remote locations. When you
assign a user group to a remote location, do not overload the remote
computer (agent). If you exceed the number of virtual users that the
remote computer can run, the performance measurements of the server
will be skewed because they will be affected by the performance of
the computer. The test results will reflect the load of the computer
more than the load of the server. For best results on a computer with
a 1 GHz processor and 1 GB of RAM, do not exceed 1000 concurrent virtual
users.
- TCP/IP ports. Your computer must have a sufficient number
of TCP/IP ports. On computers with Microsoft Windows, the typical limit is
5000. Issue the netstat -a command to observe port use. If
the largest number you see is 5000, then you need to increase the
number. To increase it, open the registry. Under HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/Tcpip/Parameters,
create a new dWord named MaxUserPort,
and set its value up to 65000. Restart the computer.
- Open file limit for Linux. Computers
that are running Linux need
a per-process open file limit higher than 1024. As root, enter ulimit
-n 30000 (or another appropriate value) before starting
Agent Controller.
- Looping within tests. If you are stress testing a server,
your test typically contains a loop. Your connection behavior differs
depending upon whether the loop is set at the schedule level or at
the test level. Setting a loop at the test, rather than the schedule,
level gives you a performance advantage, because the connections are
reused during the looping process. For more information, see Add a loop.
- Logging levels. After the test is stable, for maximum performance,
reduce the test log level and problem determination log level and
sample a small number of users. Increase the statistics sample interval
to 30 or 60 seconds for long-running tests.
- Workbench heap size. The Java™ Virtual
Machine (JVM) heap size on the workbench is based on the available
physical memory. Do not run the workbench on a computer with less
than 768 MB of physical memory. The maximum workbench heap size depends
on your JVM. Although the heap size is not strictly necessary for
playback performance, you can increase the workbench heap size. To
increase the heap size, set the -Xmx parameter in the eclipse.ini file,
which is located in the product installation directory. For Windows, if your physical memory
is 3 GB or more, then the maximum heap size must not exceed 1200 MB.
For Linux, the maximum heap
size is approximately 3000 MB. If the workbench is sluggish or fails
to start after you increase the heap size, reset the heap size to
the default by removing the VMARGS=-Xmx line
from the eclipse.ini file.
- Location (agent) heap size. To access maximum heap, after
one successful test of any size, search for a location (agent) attribute
called RPT_DEFAULT_MEMORY_SIZE. If you cannot
find this attribute, you can specify a maximum heap by creating a
new attribute: RPT_VMARGS=-Xmx1500m (for example,
max heap 1.5 GB). For more information, see Increasing memory allocation.
- Disk space. Verify that there is sufficient free disk space
on the workbench and agent computers. Also, verify that there is sufficient
free disk space on the drive that contains the system temporary directory.
- Recording length. If you record for a relatively long time,
test generation also takes a long time. If test generation is taking
a relatively long time, try shorter recording scenarios.
For more information about capacity planning, see http://www.ibm.com/support/docview.wss?uid=swg27019811.