RFR (S): 8006088: Incompatible heap size flags accepted by VM

[Thomas Schatzl]

Hi all,

  there is a new webrev for this issue at
http://cr.openjdk.java.net/~tschatzl/8006088/webrev.6/

Since it has been a while since the last update, here is a short
introduction to the problem again:

The current argument processing for minimum, initial and maximum heap
sizing is somewhat unintiutive.

This CR tries to fix and improve it.

The following problems have been identified and fixed with earlier
webrevs (as of http://cr.openjdk.java.net/~tschatzl/8006088/webrev.3):

- VM gives an error when InitialHeapSize > MaxHeapSize
- shrink NewSize and OldSize so that if MaxHeapSize is given, their sum
is below MaxHeapSize.
- automatically adapt minimum heap size if only InitialHeapSize is
given. This avoids getting "Incompatible minimum and initial heap sizes
specified" if only -XX:InitialHeapSize is specified with low values.
- also allow specification of -Xms0 (i.e. size >= 0, not size > 0); this
is a valid heap size specification, and means minimum/initial heap size
= OldSize + NewSize.
- test cases

The new additions for this webrev are as follows:

- implement the behavior shown in the table at
http://cr.openjdk.java.net/~tschatzl/8006088/webrev.6/XmsInitialHeapSizeErgo.html . This table also shows old behavior for comparison with the new behavior. Summarizing, this changeset fixes unexpected errors in the old behavior in the case when:   
  * -Xms0 is given,
  * only -XX:InitialHeapSize=0 is given (previously the resulting
initial heap size was OldSize + NewSize while now it applies normal
ergonomics), and
  * when setting -Xms to a "large" value and -XX:InitialHeapSize to
zero. (Only this issue had to be actually fixed in comparison to the
earlier webrev).
- add new jtreg tests for previously unverified behavior of that entire
table.
- improved testing for maximum heap sizing which now does not rely on a
hardcoded constant for aligning the expected value as the test case
retrieves the alignment value from the VM.

Bugs.sun.com:
http://bugs.sun.com/view_bug.do?bug_id=8006088

JIRA:
https://jbs.oracle.com/bugs/browse/JDK-8006088

Testing:
jprt, manual invocation of all test cases

Hth,
Thomas