How can I find the default MaxPermSize when -XX:+PrintFlagsFinal is not supported?

Question

I\'m working with a system where a number of jobs, implemented as Java applications, can be started simultaneously. Each job runs in a separate JVM.

Some of these jobs r

Answer 1

Default values for various regions would depend on:

• Collector being used (which would depend on Java version in case you're specifying it explicitly using CLI args).
• Sizes of heap etc you have specified using CLI args. GC would distribute the space according to some ratios.
• Installed (or may be it was available) RAM on the machine.

How to find out:

• From GC Log files (-Xloggc:gc.log), I would expect that at least in the Full GC logs, GC would report the Perm Gen sizes. See examples at bottom. You can take a representative gc log file and find the max perm gen size from it, and decide based on that.
• Additional params like PrintFlagsFinal etc. (specific to Java version)

I'll look through the 1.6 options to see if I can find something and update the post, otherwise it's time to upgrade. :-)

Here are 3 examples from different GCs (Metaspace, CMS Perm & PSPermGen is what you're looking for):

2014-11-14T08:43:53.197-0500: 782.973: [Full GC (Ergonomics) [PSYoungGen: 54477K->0K(917504K)] [ParOldGen: 1042738K->367416K(1048576K)] 1097216K->367416K(1966080K), [Metaspace: 46416K->46389K(1091584K)], 0.4689827 secs] [Times: user=3.52 sys=0.07, real=0.47 secs]
2014-10-29T06:14:56.491-0400: 6.754: [Full GC2014-10-29T06:14:56.491-0400: 6.754: [CMS: 96098K->113997K(5242880K), 0.7076870 secs] 735545K->113997K(6186624K), [CMS Perm : 13505K->13500K(51200K)], 0.7078280 secs] [Times: user=0.69 sys=0.01, real=0.71 secs] 
2014-10-29T21:13:33.140-0500: 2644.411: [Full GC [PSYoungGen: 2379K->0K(695296K)] [ParOldGen: 1397977K->665667K(1398272K)] 1400357K->665667K(2093568K) [PSPermGen: 106995K->106326K(262144K)], 1.2151010 secs] [Times: user=6.83 sys=0.09, real=1.22 secs]