• Documentation
  • Status: Closed
  • 2 Major
  • Resolution: Fixed
  • ehcache
  • qa
  • Reporter: lorban
  • August 31, 2010
  • 0
  • Watchers: 0
  • January 17, 2013
  • October 12, 2010

Description

The new offheap storage will allow for extremely large memory consumption by the JVM (dozens of GB becomes quite conceivable).

The UseLargePages JVM optimization implemented by all A-Grade JVMs may very well improve performance of applications using very large amounts of memory.

We should document the existence of this flag as well as come up with recommendations about when to use it or not.

One can read more on the subject in this article: http://developer.amd.com/documentation/articles/pages/322006145.aspx

Comments

Ludovic Orban 2010-08-31

Solaris has a command-line utility called ‘trapstat’ to help taking such decision: http://docs.sun.com/app/docs/doc/816-0211/6m6nc679d?a=view

I don’t know of an equivalent command on any other OS.

Ludovic Orban 2010-08-31

An article explaining how to use trapstat: http://www.informit.com/articles/article.aspx?p=169710

Fiona OShea 2010-08-31

Use this and see what if anything wants to be documented. That is does the setting help and if so should it be doc’d

Himadri Singh 2010-08-31

http://www.oracle.com/technetwork/java/javase/tech/largememory-jsp-137182.html

describes how to enabled large pages for diff os.

Himadri Singh 2010-08-31

Ran off heap test, it doesn’t seems to help right now.

  Case   TPS  
w/ XX:+UseLargePages 112,936      
w/o 123,370      

might need to check /proc/sys/vm/nr_hugepages, not sure what default/0 means.

Currently its been set to [email protected]:~>cat /proc/sys/vm/nr_hugepages
0

Ludovic Orban 2010-08-31

Do we have any Solaris and/or Windows Server 2003 test machines?

Kalai Kannaiyan 2010-08-31

Yes, We have Solaris 9 (dev08 and dev09) and Windows Server 2003 (devV07)

gluck 2010-10-12

UseLargePages is already documented on off-heap.apt. More can be added as we learn more.