RFR: JDK-8016309 - assert(eden_size > 0 && survivor_size > 0) failed

Jesper Wilhelmsson jesper.wilhelmsson at oracle.com
Thu Sep 19 14:38:48 PDT 2013


Could I have a couple of reviews of this cleanup/bugfix.

The bug I intended to fix is JDK-8016309 [1] in which the eden size could end up 
with a zero size due to minimum alignment and a too small young gen size.
The alignment was increased in the fix for JDK-6725714 [2] which caused this bug.

Fixing this in the current collector policies was quite messy. Attempts to fix 
this issue is actually already implemented in two different places, none of them 
results in a properly sized eden. Since Thomas had a patch to cleanup the 
collector policies to fix JDK-7057939 [3], I based my bugfix on his patch 
instead of fighting with the mess in the current collector policies. As Thomas 
wasn't actively working on finishing his cleanup patch I also continued that 
work to finish it.

This cleanup fixes both bugs (JDK-8016309 and JDK-7057939). To extract them to 
different patches would be too much work and result in an intermediate state 
between the two patches where the ergonomics wouldn't work properly. I have 
however split the webrev into two parts:

The first patch contains cosmetic changes (name changes, being consequent in 
using local instance variables vs using getters/setters, fixing typos in 
comments etc.).


The second patch contains the major part of the cleanup work in the collector 
policies. The goal has been to make the code easier to follow and pull policy 
decisions that had leaked into other code back to the collector policy classes.


Please note that the default value of NewSize has changed from 1M to 2M. Since 
the minimum alignment was increased to 512K, the minimal possible young gen size 
increased to 1.5M. Having a smaller default would be miss leading as the 
ergonomics would increase it every time.

New tests has been added and all existing jtreg arguments tests has been used to 
verify that heap sizing ergonomics behaves as expected.

Minor note:
The method GenCollectedHeap::compute_new_generation_sizes was unused. In the 
cleanup patch I have commented it out in case anyone left it there on purpose. 
I'd prefer to remove it. (Actually the second patch removes the method unless 
someone really wants to keep it.)


[1] https://bugs.openjdk.java.net/browse/JDK-8016309
[2] https://bugs.openjdk.java.net/browse/JDK-6725714
[3] https://bugs.openjdk.java.net/browse/JDK-7057939

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