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From "Geir Magnusson Jr." <g...@pobox.com>
Subject Re: [DRLVM][MMTk GC] marksweep configuration works in "user mode"
Date Wed, 30 Aug 2006 04:39:22 GMT


Weldon Washburn wrote:
> All,
> 
> I just committed mods that allow MMTk marksweep configuration to run
> the simple tests in test.java.
> 

That's cool - what do we do with it next? :)

geir

> There were some workarounds in MMTk code itself.  It does not make
> sense to commit these workarounds to drlvm/trunk or to put them in
> JIRA.  Instead, I told Steve Blackburn what the MMTk porting problems
> are.
> 
> For the record the MMTk mods are:
> 
> 1)
> SegregatedFreeList.java wants to use vmmagic atomic operations even in
> single java thread app.  But vmmagic atomic ops are not fully
> functional in Jitrino.JET just yet.  The workaround is to do a simple
> write to memory instead of CAS.  The mods to SegregatedFreeList.java
> are:
> 731a732
>>       atomic = false;  //wjw hack around Addresss.attempt bug
> 
> 2)
> MMType.getSlot() is hard coded to assume that element zero is an
> "Offset" of zero from the vtable ptr.  While this may indeed be the
> case for JikesRVM, in DRLVM the offset is 12.  The diff to MMType.java
> is:
> 83,86c83,86
> <     if (isReferenceArray)
> <       return addr.plus(arrayOffset).plus(reference << 
> LOG_BYTES_IN_ADDRESS);
> <     else
> <       return addr.plus(offsets[reference]);
> ---
>>       if (isReferenceArray)
>>           return addr.plus(12).plus(reference << 
>> LOG_BYTES_IN_ADDRESS);  // return 
>> addr.plus(arrayOffset).plus(reference << LOG_BYTES_IN_ADDRESS);
>>       else
>>           return addr.plus(offsets[reference]);
> 
> 
> 

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