JVM options

[Claudio Nieder]

Hi,

> That doesn't appear to be working with the openjdk 7 build.

$ java -showversion -XX:+PrintGC -XX:+PrintGCDetails C
java version "1.7.0_11"
Java(TM) SE Runtime Environment (build 1.7.0_11-b21)
Java HotSpot(TM) 64-Bit Server VM (build 23.6-b04, mixed mode)

[GC [PSYoungGen: 17600K->464K(20480K)] 17600K->464K(67200K), 0.0012910 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
 ...
[GC [PSYoungGen: 373469K->159K(373632K)] 373825K->516K(420352K), 0.0003640 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
Heap
 PSYoungGen      total 373632K, used 14955K [0x0000000136be0000, 0x000000014d930000, 0x000000014d930000)
  eden space 373312K, 3% used [0x0000000136be0000,0x0000000137a52ec0,0x000000014d870000)
  from space 320K, 49% used [0x000000014d8c0000,0x000000014d8e7ff0,0x000000014d910000)
  to   space 320K, 0% used [0x000000014d870000,0x000000014d870000,0x000000014d8c0000)
 ParOldGen       total 46720K, used 356K [0x0000000109130000, 0x000000010bed0000, 0x0000000136be0000)
  object space 46720K, 0% used [0x0000000109130000,0x0000000109189060,0x000000010bed0000)
 PSPermGen       total 21248K, used 2639K [0x0000000103f30000, 0x00000001053f0000, 0x0000000109130000)
  object space 21248K, 12% used [0x0000000103f30000,0x00000001041c3df0,0x00000001053f0000)

Did you copy the options from that webpage verbatim? I notice, that it says there e.g.

-XX:-PrintGCDetails	Print more details at garbage collection.

Now PrintGCDetails is a boolean flag, and the sign between -XX: and PrintGCDetails is +/- depending on whether you want to switch it on or off. It is unfortunate, that on that page the "-" is set. Maybe to indicate that by default this is switched off. When you use it you have to put a + in there as I did on my example.

claudio
-- 
Claudio Nieder, Talweg 6, CH-8610 Uster, Tel +4179 357 6743, www.claudio.ch