Re: [rvm-research] Regarding Address of Object Reference in Field section of Object

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The Poisoned collector in current hg tip works for me in BaseBase,
FullAdaptive and FastAdaptive configurations, at least for the handful
of dacapo 2006 benchmarks I looked at.

The Poisoned heap collector is also included in the nightly sanity
checks, and gets 98%+ success, so odds are its either a stray change
in your code base or something to do with your environment.

Which version of JikesRVM are you building ?  What environment ?  What
benchmark are you running ? Can you double-check that there are no
changes to the code base, and do a fresh build ?

cheers
Robin

On 14/01/14 18:18, Hari Krishnan wrote:
> Rifat,
> 
> The seg fault is thrown for poisoned implementation also. Not just
> for my implementation. I hope you can let me know why  this is
> happening. Thank you.
> 
> 
> On Tue, Jan 14, 2014 at 12:55 AM, Hari Krishnan
> <[email protected] <mailto:[email protected]>> wrote:
> 
> Rifat,
> 
> When I add in the constraints class to return true for the
> specified method, the rvm when executing is giving a seg fault.
> 
> 
> Cheers Hari
> 
> 
> On Tue, Jan 14, 2014 at 12:16 AM, Rifat Shahriyar 
> <[email protected] <mailto:[email protected]>>
> wrote:
> 
> You need to set the constraint needsObjectReferenceReadBarrier() to
> true. Look at PoisonedConstraints.
> 
> Regards - Rifat
> 
> 
> On 14/01/2014 5:11 pm, Hari Krishnan wrote:
>> Robin,
>> 
>> Thank you. I am looking at that code.  When I override 
>> objectReferenceRead it seems like it is never called. I am trying
>> to understand how it works. Is there anything I have to do other
>> than overriding that in my mutator class?
>> 
>> Cheers Hari Krishnan.
>> 
>> 
>> On Mon, Jan 13, 2014 at 11:47 PM, Robin Garner 
>> <[email protected] <mailto:[email protected]>> wrote:
>> 
> The MMTk plan "poisoned" unconditionally sets and clears the
> low-order bit of all object references - this is the regression
> test for object read and write barriers.
> 
> cheers
> 
> On 14/01/14 15:53, Hari Krishnan wrote:
>> Robin,
> 
>> The process is basically to mark the references as I
> trace the
>> objects. Since I want to mark the instance field
> references in each
>> object, I want to mutate a single bit indicating the
> reference is
>> processed.  So yes to question (you want to add a single
> bit of
>> metadata to each object reference ?).Thank you for your
> help. I
>> want to try Read Barriers. I appreciate your quick
> response. Is
>> there any code that  already overrides read barrier?
> 
>> Cheers Hari Krishnan.
> 
> 
>> On Mon, Jan 13, 2014 at 10:45 PM, Robin Garner 
>> <[email protected] <mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>>
> wrote:
> 
>> Hari,
> 
>> Just to clarify, you want to add a single bit of
> metadata to each
>> object reference ?
> 
>> The "simplest"[1] solution is to use one of the two
> low-order bits
>> of each object reference (objects are always (at least)
> 4-byte
>> aligned). In order to do this you'll need a read barrier
> that masks
>> out this bit so that the mutator always sees aligned
> pointers, and
>> a write barrier that reinstates the metadata.
> 
>> Alternatively, if this is too expensive, I'd suggest adding 
>> additional space to the object via the classloader - how
> easy this
>> is depends on how you want to use the data, how much
> space you're
>> prepared to use etc.
> 
>> cheers
> 
>> [1] Read barriers are never simple :-/
> 
>> On 14/01/14 12:01, Hari Krishnan wrote:
>>> Hi ,
> 
>>> I want to set a bit, toggle a bit and test a bit in the
> section
>>> where each address of the instance field (object
> references)
>>> saved in objects. Is there any bit that I can use in
> each object
>>> fields for this purpose?
> 
>>> Cheers Hari Krishnan
> 

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