RFR: 8152113: Remove _last_ditch_collection GC-cause and avoid expanding heap on Metaspace OOM

Stefan Johansson stefan.johansson at oracle.com
Mon Mar 21 08:16:55 UTC 2016

Thanks for the review Jon,

On 2016-03-18 18:01, Jon Masamitsu wrote:
> Looks good.
> Jon
> On 3/17/2016 10:03 AM, Stefan Johansson wrote:
>> Hi,
>> Please review this change for RFE:
>> https://bugs.openjdk.java.net/browse/JDK-8152113
>> Webrev:
>> http://cr.openjdk.java.net/~sjohanss/8152113/hotspot.00/
>> Summary:
>> Prior to this patch the GC-cause _last_ditch_collection has been used 
>> for 2 types of full-collections that clears soft references:
>> 1. Last resort when out of metaspace memory
>> 2. WhiteBox initiated full GC
>> These have not much in common and the GC-cause is strangely named 
>> when looking at its meaning. This cause also comes with an unwanted 
>> side-effect, it will expand the heap if possible and this is strange 
>> since it is not caused by a failed heap-allocation. This change 
>> removes the _last_ditch_collection cause and now we instead use two 
>> separate causes, _wb_full_gc for the WhiteBox-case and 
>> _metadata_GC_clear_soft_refs for the out of metaspace case. The idea 
>> is that these will work similar to _last_ditch_collection in every 
>> way except when it comes to growing the heap.
>> Testing:
>> Run several tonga test-lists in RBT with G1, CMS and Parallel without 
>> seeing any new issues.
>> Thanks,
>> Stefan

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