Re: [rvm-research] [rvm-core] Regarding MMTK

Hello,
I believe you are using reference counting (RC). RC in Jikes RVM don't 
use any extra word to store the reference count, rather it uses 4 bits 
from the available byte to store the count. That is why 
/GC_HEADER_WORDS_REQUIRED/ are set to 0. If you need extra words then 
you need to update /GC_HEADER_WORDS_REQUIRED/. After that you can read 
the words with appropriate offsets. For example,

public static final Offset RC1_HEADER_OFFSET = 
VM.objectModel.GC_HEADER_OFFSET()  // /offset for the first extra word/
object.toAddress().prepareWord(RC1_HEADER_OFFSET) // /atomically read 
the word/
object.toAddress().loadWord(RC1_HEADER_OFFSET) // /non-atomic read/
object.toAddress().attempt(oldValue, newValue, RC1_HEADER_OFFSET) // 
/atomically write the word//with prepare//
/object.toAddress().store(value, RC1_HEADER_OFFSET) // /non-atomic write/

For the next word you need to use the following offset to read/write
public static final Offset RC2_HEADER_OFFSET = 
RC1_HEADER_OFFSET.plus(BYTES_IN_WORD)  // /offset for the next extra word/


Regards
-
Rifat

On 19/11/2013 10:27 pm, Hari Krishnan wrote:
> Hi,
>
> I have a question about MMTK. I want my GC Header to be 4 words size. 
> I see the change in the size of each object allocation that 4 words 
> are allocated for GC Header but I cannot mutate those words. The 
> method prepareavailableword() , readavailableword(), 
> writeavailableword() works only  on one word in GCHeader. How do I 
> read and write this 4 word sized GC Header?
>
> Cheers,
> Hari Krishnan
>
>
> ------------------------------------------------------------------------------
> Shape the Mobile Experience: Free Subscription
> Software experts and developers: Be at the forefront of tech innovation.
> Intel(R) Software Adrenaline delivers strategic insight and game-changing
> conversations that shape the rapidly evolving mobile landscape. Sign up now.
> http://pubads.g.doubleclick.net/gampad/clk?id=63431311&iu=/4140/ostg.clktrk
>
>
> _______________________________________________
> Jikesrvm-core mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/jikesrvm-core

------------------------------------------------------------------------------
Shape the Mobile Experience: Free Subscription
Software experts and developers: Be at the forefront of tech innovation.
Intel(R) Software Adrenaline delivers strategic insight and game-changing 
conversations that shape the rapidly evolving mobile landscape. Sign up now. 
http://pubads.g.doubleclick.net/gampad/clk?id=63431311&iu=/4140/ostg.clktrk

_______________________________________________
Jikesrvm-researchers mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/jikesrvm-researchers