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From "Xiao-Feng Li" <xiaofeng...@gmail.com>
Subject Re: [DRLVM] what's the purpose to set NEXT_TO_HIGH_BIT_SET_MASK in object size?
Date Wed, 21 Mar 2007 12:52:55 GMT
Pavel, Thanks for your reply.

Would let me know how NEXT_TO_HIGH_BIT is used currently in DRLVM? Or
in other words, what functionalities are dependent on
NEXT_TO_HIGH_BIT?

Thanks,
xiaofeng

On 3/21/07, Pavel Pervov <pmcfirst@gmail.com> wrote:
> Xiao-Feng,
>
> All the infructructure is in place. It is just do not work at the moment.
> As Class.newInstance is not native, NSO does not replace it's implementation
> with VM's stub.
> If NEXT_TO_HIGH_BIT-supporting code is to be removed, the rest of the code
> (NSO implementations for ia32 and ia64) has to be removed altogether to not
> provoke any errors in the future.
>
> Does removing NSO overrides for Class.newInstance look reasonable for you?
>
> WBR,
>     Pavel.
>
> On 3/21/07, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> >
> > If no one objects, I will try to remove this flag in DRLVM.
> >
> > Thanks,
> > xiaofeng
> >
> > On 3/21/07, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> > > Hi, the source code for class preparation calls
> > > set_instance_data_size_constraint_bit() for three situations: special
> > > alignment requirement, having finalizer, and to be pinned. And the
> > > comments there say the constraint bit is for GC to understand.
> > >
> > > But current GC actually doesn't care about this bit, and simply masks
> > > it off. Does anybody know what are the situations for the size
> > > constraint bit to be set for allocation?
> > >
> > > I recall this kind of constraint bit was ORP legacy, when the
> > > intention was for gc_alloc_fast to be really fast, avoiding any
> > > special allocation treatment. So once the big flag is set,
> > > gc_alloc_fast will simply return NULL, and the VM will invoke gc_alloc
> > > to accomplish the allocation.
> > >
> > > Now DRLVM has different processing, and the GC doesn't use the flag in
> > > size for allocation. I wonder what is the real purpose of this size
> > > flag in allocation.
> > >
> > > Thanks,
> > > xiaofeng
> > >
> >
>
>
>
> --
> Pavel Pervov,
> Intel Enterprise Solutions Software Division
>

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