Question

In the document(jbossperformancetuning.pdf), it suggest us to enable large page memory for the JVM.

But actually after I added the following to our command-line / script start-up:
“-XX:+UseLargePages”

It didn’t work, so I investigated more, enabled the large page memory on OS first, then added “-XX:+UseLargePages -XX:LargePageSizeInBytes=2m” to start-up script.

But unfortunately, it didn’t work neither, so could someone give us some suggestions of how to enable the large page memory for the JVM successfully?

Here are some details of our server:

[root@localhost ~]# cat /proc/meminfo

MemTotal:     37033340 kB
MemFree:        318108 kB
Buffers:        179452 kB
Cached:        5934940 kB
SwapCached:          0 kB
...
HugePages_Total: 10251
HugePages_Free:  10251
HugePages_Rsvd:      0
Hugepagesize:     2048 kB

[root@localhost ~]# ps aux | grep java

root     22525  0.2 20.3 28801756 7552420 ?    Sl   Nov03  31:54 java -Dprogram.name=run.sh -server -Xms1303m -Xmx24g -XX:MaxPermSize=512m -XX:+UseLargePages -XX:LargePageSizeInBytes=2m -Dorg.jboss.resolver.warning=true -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000 -Dsun.lang.ClassLoader.allowArraySyntax=true -verbose:gc -Xloggc:/tmp/gc.log -XX:+PrintGCDetails -XX:+PrintGCDateStamps -Djava.net.preferIPv4Stack=true -Djava.endorsed.dirs=/opt/jboss-as/lib/endorsed -classpath /opt/jboss-as/bin/run.jar org.jboss.Main -c default -b 0.0.0.0
root     31962  0.0  0.0  61200   768 pts/2    S+   22:46   0:00 grep java

[root@localhost ~]# cat /etc/sysctl.conf

...
# JBoss is running as root, so the group id is 0
vm.hugetlb_shm_group = 0
# The pages number
vm.nr_hugepages = 12288

Answer 1

Finally I fixed this issue, at first set the large pages memory bigger than JVM heap size, then just reboot the server, because there is no way to make it work unless you upgrade the kernel to the newer one – in RHEL 6.0.