Weldon, the bits your mentioned are for obj_info. Vtable can't have its bits overloaded simply without special handling.
Thanks, xiaofeng On 8/24/06, Weldon Washburn <[EMAIL PROTECTED]> wrote:
On 8/23/06, Xiao-Feng Li <[EMAIL PROTECTED]> wrote: > Weldon, I experimented with last two bits for marking and forwarding > without problem. I assume you are referring to the 2 lowest bits in the vtable pointer. The two lowest bits will step on the recursion mask in sync_bits.h... won't it? I am confused. It turns out that MMTk keeps the mark bits around even between GCs. Leaving an LSB of the vtable ptr set and then resuming application execution will surely cause a failure. Thus there needs to be a full time dedicated mark bit in the object header. This is in addition to the need for a forwarding bit. > > The GC_OBJECT_MARK_BIT_MASK is for obj_info field, not the vt field. ( > So far as I experimented, it's only used for heap verification). > > Thanks, > xiaofeng > > On 8/24/06, Weldon Washburn <[EMAIL PROTECTED]> wrote: > > Looking at drlvm/trunk, it looks like vmcore/include/sync_bits.h > > defines the use of *(ref_ptr +4) for 32-bit environment. Just > > guessing that "#define BUSY_FORWARDING_OFFSET 0" is intended to tell > > the GC that it can use the least significant bit out of these four > > bytes. Is this correct? I would like to use this bit as an MMTk mark > > bit. Will this work? (Actually the name, BUSY_FORWARDING_OFFSET is > > probably not the best...) > > > > There is also a gc/src/gc_header.h file that contains, "#define > > GC_OBJECT_MARK_BIT_MASK 0x80". This seems to step on top of > > sync_bits.h use of this area??? Can I assume gc_header.h is > > incorrect? > > > > -- > > Weldon Washburn > > Intel Middleware Products Division > > > > --------------------------------------------------------------------- > > Terms of use : http://incubator.apache.org/harmony/mailing.html > > To unsubscribe, e-mail: [EMAIL PROTECTED] > > For additional commands, e-mail: [EMAIL PROTECTED] > > > > > > --------------------------------------------------------------------- > Terms of use : http://incubator.apache.org/harmony/mailing.html > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > > -- Weldon Washburn Intel Middleware Products Division --------------------------------------------------------------------- Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
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