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WEBSPHERE PORTAL V6.1 TUNING GUIDE
J V M H E A P L A R G E P A G E
Large pages can reduce the CPU overhead needed to keep track of heap. With this setting
we have seen 10% throughput improvement in our measurements.
This setting does improve performance on Windows, we did not set it for our measurements because
Portal doesn’t start reliably when –Xlp is set, sometimes it requires a system reboot to get the jvm to
start.
How-to Set: In the WebSphere Administrative Console: Servers -> Application Servers ->
WebSphere Portal -> Server Infrastructure: Java and Process Management -> Process Definition ->
Java Virtual Machine -> Generic JVM Argument. Add –Xlp.
Large pages are supported by systems running Linux kernels V2.6 or higher. See JVM
Large Page Tuning for AIX Operation System.
JVM LARGE PAGE TUNING O N AIX O PER ATING SYS TEM
To use JVM Large Page, AIX operating system must be configured to support large pages.
How-To Set:
1. We use the following steps to allocate 4GB of RAM as large pages (16MB) . We chose
this amount based on having 8GB of physical memory in these systems. These values
may need to be adjusted on systems with different amounts of physical memory.
vmo -r -o lgpg_regions=256 -o lgpg_size=16777216
bosboot -ad /dev/ipldevice
reboot -q
vmo -p -o v_pinshm=1
chuser capabilities=CAP_BYPASS_RAC_VMM,CAP_PROPAGATE $USER
2. Add: -Xlp command-line option as described above.
3. In the WebSphere Administrative Console: Servers Application Servers
WebSphere Portal Server Infrastructure: Java and Process ManagementProcess
Definition-> Environment Entries New EXTSHM=OFF (note: When EXTSHM is
on it prevents use of large page).
4. Restart Portal Server. To verify if large pages are being used, run the AIX command
vmstat -l 1 5 and check the "alp" column which is the active large page used. It should
be a non-zero value if large pages are being used.
Parameter AIX
POWER5
Linux
Solaris
Windows
2003
z/Linux z/OS
JVM Heap
Large page
-Xlp -Xlp Not
Applicable
Not
Applicable
Not
Applicable
Not
Applicable