Preventing Class Definitions from Compacting At GC Cycle

姜善林 jiangshanlin at
Mon Nov 4 01:40:34 UTC 2013

Hi all,

I'm sorry if this email bothers you. Just one question, is there any way to
determine precisely the regression test scope for java development and

Many thanks!

2013/11/4 David Holmes <david.holmes at>

> Adding hotspot-gc and (hopefully) bcc'ing the discuss list.
> David
> On 3/11/2013 5:18 AM, serkan özal wrote:
>> Hi all,
>> I am not sure that target of mail is this group or not but I don't know
>> better one for asking :)
>> I am currently working on an OffHeap solution and I have a problem with
>> "Compact" phase of GC.As I see at "Compact" phase, location of classes
>> these not loaded by bootloader may be changed. However, location of classes
>> these loaded by bootloader (classloaders are null) are not changed.Changing
>> memory location of class definition fails my OffHeap solution.
>> Compacting can be disabled by VM arguments but I don't want to use these
>> arguments. Because disabling compaction for all objects causes increasing
>> of fragmentation. In addition, I tried class pinning with JNI by
>> "NewGlobalRef" method but it doesn't prevent compacting. As I understood,
>> it only hides object from garbage collected.
>> In brief, is there any way to prevent compacting of any specific class
>> defition (or object) at GC cycle?Is there any bit, offset or field (such as
>> mark_oop) in object header to prevent compacting of fully from GC for any
>> specific object or class?
>> Thanks in advance.
>> --
>> Serkan ÖZAL

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