Weird heap allocation

Question

Hi everybody,
It seems that our jrockit is creating huge heaps even for the simplest programs. Check out the following data.
OS: RedHat EL 4.0 x86_64
Java: JRockit R27.3.1 x86_64
Say we run the following program:
public class TestHeap {
  public static void main(String[] args) throws InterruptedException {
  System.out.println("Sleeping");
  Thread.sleep(600000);
  System.out.println("Finished");
}I run jrcmd print_memusage on that process and this is the weird output:
[JRockit] *** 0th memory utilization report
(all numbers are in kbytes)
Total mapped ;;;;;;;3304980
; Total in-use ;;;;;; 141076
;; executable ;;;;; 5436
;;; java code ;;;; 384; 7.1%
;;;; used ;;; 235; 61.4%
;; shared modules (exec+ro+rw) ;;;;; 5031
;; guards ;;;;; 144
;; readonly ;;;;; 47448
;; rw-memory ;;;;; 88576
;;; Java-heap ;;;; 65536; 74.0%
;;; Stacks ;;;; 4552; 5.1%
;;; Native-memory ;;;; 18487; 20.9%
;;;; java-heap-overhead ;;; 2057
;;;; codegen memory ;;; 768
;;;; classes ;;; 2816; 15.2%
;;;;; method bytecode ;; 196
;;;;; method structs ;; 424 (#5438)
;;;;; constantpool ;; 1101
;;;;; classblock ;; 128
;;;;; class ;; 231 (#439)
;;;;; other classdata ;; 349
;;;;; overhead ;; 189
;;;; threads ;;; 16; 0.1%
;;;; malloc:ed memory ;;; 1545; 8.4%
;;;;; codeinfo ;; 75
;;;;; codeinfotrees ;; 48
;;;;; exceptiontables ;; 10
;;;;; metainfo/livemaptable ;; 222
;;;;; codeblock structs ;; 0
;;;;; constants ;; 0
;;;;; livemap global tables ;; 226
;;;;; callprof cache ;; 0
;;;;; paraminfo ;; 32 (#467)
;;;;; strings ;; 460 (#7653)
;;;;; strings(jstring) ;; 0
;;;;; typegraph ;; 54
;;;;; interface implementor list ;; 10
;;;;; thread contexts ;; 14
;;;;; jar/zip memory ;; 425
;;;;; native handle memory ;; 12
;;;; unaccounted for memory ;;; 11300; 61.1%;7.31
So this makes 3Gb of.... nothing. why is that memory being allocated? is there a way to change this weird behaviour?
Thanks,
Martin

Answer 1

Some more info on this. If I run that hello world program with -Xmx64M i get the following output (btw, machine has 4Gb).
[JRockit] *** 0th memory utilization report
(all numbers are in kbytes)
Total mapped ;;;;;;;1201940
; Total in-use ;;;;;; 133140
;; executable ;;;;; 5436
;;; java code ;;;; 384; 7.1%
;;;; used ;;; 235; 61.4%
;; shared modules (exec+ro+rw) ;;;;; 5031
;; guards ;;;;; 144
;; readonly ;;;;; 47448
;; rw-memory ;;;;; 80640
;;; Java-heap ;;;; 65536; 81.3%
;;; Stacks ;;;; 4552; 5.6%
;;; Native-memory ;;;; 10551; 13.1%
;;;; java-heap-overhead ;;; 2057
;;;; codegen memory ;;; 768
;;;; classes ;;; 2816; 26.7%
;;;;; method bytecode ;; 196
;;;;; method structs ;; 424 (#5438)
;;;;; constantpool ;; 1101
;;;;; classblock ;; 128
;;;;; class ;; 231 (#439)
;;;;; other classdata ;; 349
;;;;; overhead ;; 189
;;;; threads ;;; 16; 0.2%
;;;; malloc:ed memory ;;; 1545; 14.6%
;;;;; codeinfo ;; 75
;;;;; codeinfotrees ;; 48
;;;;; exceptiontables ;; 10
;;;;; metainfo/livemaptable ;; 222
;;;;; codeblock structs ;; 0
;;;;; constants ;; 0
;;;;; livemap global tables ;; 226
;;;;; callprof cache ;; 0
;;;;; paraminfo ;; 32 (#467)
;;;;; strings ;; 460 (#7653)
;;;;; strings(jstring) ;; 0
;;;;; typegraph ;; 54
;;;;; interface implementor list ;; 10
;;;;; thread contexts ;; 14
;;;;; jar/zip memory ;; 425
;;;;; native handle memory ;; 12
;;;; unaccounted for memory ;;; 3364; 31.9%;2.18
---------------------!!!