Bug ID: JDK-6524727 GC ergonomics does not honor the minimum young gen size implied by a -Xms and NewRatio

Type: Bug
Component: hotspot
Sub-Component: gc
Affected Version: 5.0,7

Priority: P3
Status: Resolved
Resolution: Fixed
OS: generic
CPU: generic

Submitted: 2007-02-13
Updated: 2010-08-28
Resolved: 2007-05-24

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Other	Other	JDK 6	JDK 7	Other
5.0u22-rev,hs10Fixed	5.0u23Fixed	6u4Fixed	7Fixed	hs10Fixed

Using -Xms and NewRatio does not set the correct minimum size for
the young generation when GC ergonomics is being used.  The minimum size
for the young generation is still set by NewSize which has not been
adjusted for -Xms.

WORK AROUND The minimum size of the young gen needs to be explicitly set. The comment on the workaround should say to set NewSize (not NewRatio).
28-08-2010
SUGGESTED FIX Added a variable (_min_heap_byte_size) to hold the minimum size of the heap and use it to set the minimum size of the young generation.
22-02-2007
EVALUATION The parallel collector uses NewSize as the minimum size of the young generation and does not check the size implied by -Xms and NewRatio. The fix is to check the value implied by -Xms and NewRatio and use the larger between it and NewSize if NewSize has not been explicitly set on the command line. With the other collectors the minimum sizes and the initial sizes of the generations are the same and the initial size for the young generation is correctly set according to -Xms and NewRatio where it needs to be.
22-02-2007
WORK AROUND Explicitly setting NewRatio or using -Xmn does the right thing.
13-02-2007

Relates :	JDK-6566474 - PS: In the UseParallelGC collector the minimum gen0 size can exceed the maximum gen0 size.
Relates :	JDK-6527727 - Sizing parameters: Sole starting/minimum spec should bound default choice of maximum from below
Relates :	JDK-6924306 - min heap size should set to initial heap size in case max heap greater than minimun new size.
Relates :	JDK-6822429 - configuration anomaly in JRE 6 wrt NewSize parameter: JVM refuses to start