$ java -version
java version "1.6.0_25"
Java(TM) SE Runtime Environment (build 1.6.0_25-b06)
Java HotSpot(TM) 64-Bit Server VM (build 20.0-b11, mixed mode)
$ java -XX:+PrintFlagsFinal TestThreadStackSize | grep 'intx ThreadStackSize'
     intx ThreadStackSize                           = 1024            {pd product}
$ java -Xss2m -XX:ThreadStackSize=3k -XX:+PrintFlagsFinal TestThreadStackSize | grep 'intx ThreadStackSize'
     intx ThreadStackSize                          := 3072            {pd product}
$ java -XX:ThreadStackSize=3k -Xss2m -XX:+PrintFlagsFinal TestThreadStackSize | grep 'intx ThreadStackSize'
     intx ThreadStackSize                          := 2048            {pd product}

=>0x00007f321801b800 JavaThread "Thread-0" [_thread_in_vm, id=26066, stack(0x00007f321d770000,0x00007f321d871000)]
// 1MB stack + 4KB guard page
  0x00000000403ba800 JavaThread "main" [_thread_blocked, id=26053, stack(0x00007f32233e9000,0x00007f32234ea000)]
// 1MB stack + 4KB guard page

=>0x00007fb14801c800 JavaThread "Thread-0" [_thread_in_vm, id=26153, stack(0x00007fb14d490000,0x00007fb14d791000)]
// 3MB stack + 4KB guard page
  0x000000004016f800 JavaThread "main" [_thread_blocked, id=26140, stack(0x00007fb153c0a000,0x00007fb153e0b000)]
// 2MB stack + 4KB guard page

=>0x00007f2ea0036800 JavaThread "Thread-0" [_thread_in_vm, id=26171, stack(0x00007f2ea649f000,0x00007f2ea66a0000)]
// 2MB stack + 4KB guard page
  0x0000000040edf800 JavaThread "main" [_thread_blocked, id=26158, stack(0x00007f2eac719000,0x00007f2eac91a000)]
// 2MB stack + 4KB guard page