FULL PRODUCT VERSION :
java version "1.6.0_14"
Java(TM) SE Runtime Environment (build 1.6.0_14-b08)
Java HotSpot(TM) Client VM (build 14.0-b16, mixed mode)

FULL OS VERSION :
Linux strongbad 2.6.28-13-generic #44-Ubuntu SMP Tue Jun 2 07:55:09 UTC 2009 x86_64 GNU/Linux

Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
-XX:NewRatio does not work at all in combination with -XX:+UseConcMarkSweepGC

The docs don't list any limitations on the use of NewRatio - in fact, they suggest that it be used in certain cases.

http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html

With default GC, and NewRatio set to 3, and MaxHeap set to 600 MB, I would expect my new generation space to be somewhere around 200 MB.

Working Example:

 =>/opt/java/jre_x32_1.6.0_14/bin/java -server -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:NewRatio=3 -Xms600M -Xmx600M -version

-XX:MaxHeapSize=629145600 -XX:NewRatio=3 -XX:ParallelGCThreads=2 -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:+UseParallelGC
java version "1.6.0_14"
Java(TM) SE Runtime Environment (build 1.6.0_14-b08)
Java HotSpot(TM) Server VM (build 14.0-b16, mixed mode)
Heap
 PSYoungGen total 134400K, used 2304K [0xeaa40000, 0xf4040000, 0xf4040000)
  eden space 115200K, 2% used [0xeaa40000,0xeac80010,0xf1ac0000)
  from space 19200K, 0% used [0xf2d80000,0xf2d80000,0xf4040000)
  to space 19200K, 0% used [0xf1ac0000,0xf1ac0000,0xf2d80000)
 PSOldGen total 460800K, used 0K [0xce840000, 0xeaa40000, 0xeaa40000)
  object space 460800K, 0% used [0xce840000,0xce840000,0xeaa40000)
 PSPermGen total 16384K, used 1431K [0xca840000, 0xcb840000, 0xce840000)
  object space 16384K, 8% used [0xca840000,0xca9a5c88,0xcb840000)

I end up with 134400K - perfectly reasonable. The ratio is 134400 / 460800 = .29 - just shy of the 1:3 ratio I was asking for.

Failing example - same command as above, except now, adding CMS:

 =>/opt/java/jre_x32_1.6.0_14/bin/java -server -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:NewRatio=3 -Xms600M -Xmx600M -XX:+UseConcMarkSweepGC -version

-XX:MaxHeapSize=629145600 -XX:MaxNewSize=33554432 -XX:MaxTenuringThreshold=4 -XX:NewRatio=3 -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:+UseConcMarkSweepGC -XX:+UseParNewGC
java version "1.6.0_14"
Java(TM) SE Runtime Environment (build 1.6.0_14-b08)
Java HotSpot(TM) Server VM (build 14.0-b16, mixed mode)
Heap
 par new generation total 29504K, used 524K [0xca770000, 0xcc770000, 0xcc770000)
  eden space 26240K, 2% used [0xca770000, 0xca7f3340, 0xcc110000)
  from space 3264K, 0% used [0xcc110000, 0xcc110000, 0xcc440000)
  to space 3264K, 0% used [0xcc440000, 0xcc440000, 0xcc770000)
 concurrent mark-sweep generation total 581632K, used 0K [0xcc770000, 0xeff70000, 0xeff70000)
 concurrent-mark-sweep perm gen total 16384K, used 1431K [0xeff70000, 0xf0f70000, 0xf3f70000)

And I get 29504K. 29504 / 581632 = .05 = or a ratio of 1:20.

You will also notice from the output of PrintCommandLineFlags that the VM has decided to set -XX:MaxNewSize=33554432, even though I did not specify it on the command line.


Same broken behaviour on Linux and Windows.




THE PROBLEM WAS REPRODUCIBLE WITH -Xint FLAG: Did not try

THE PROBLEM WAS REPRODUCIBLE WITH -server FLAG: Yes

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
See description.

EXPECTED VERSUS ACTUAL BEHAVIOR :
Use the NewRatio flag as documented.


REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
-XX:NewSize=xx works as expected.