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From "Pavel Pervov" <pmcfi...@gmail.com>
Subject Re: [DRLVM] what's the purpose to set NEXT_TO_HIGH_BIT_SET_MASK in object size?
Date Thu, 22 Mar 2007 09:02:16 GMT
I mean, if there were three conditions to fall back to slow allocation and
now there is only one such condition, is this right or it is the issue in
harmony code which should be fixed ASAP?

On 3/22/07, Pavel Pervov <pmcfirst@gmail.com> wrote:
>
> It is used in native override for Class.newInstance to overflow allocation
> limit in fast path and fall back to slow allocation (which ignores this bit
> set, as you've mentioned earlier). Class.newInstance is not native though
> and this code simply does not work right now.
>
> The only property gc now treats as "not-possible-to-allocate-fast" is
> "class has finalize method".
> Is this correct from algorithmic POV?
>
> WBR,
>     Pavel.
>  On 3/22/07, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> >
> > Pavel, thanks. Since the semantic of newInstance or alloc_instance or
> > gc_alloc(_fast) itself doesn't actually use NEXT_TO_HIGH_BIT, no
> > matter it is written in Java or other languages, I think NSO will not
> > use it either. Do you think so? Or would you tell me how NSO will use
> > NEXT_TO_HIGH_BIT?
> >
> > Thanks,
> > xiaofeng
> >
> > On 3/21/07, Pavel Pervov < pmcfirst@gmail.com> wrote:
> > > "is now implemented" it was supposed to be written. :)
> > >
> > > On 3/21/07, Pavel Pervov < pmcfirst@gmail.com> wrote:
> > > >
> > > > It is indirectly used in the NSO for Class.newInstance. But this
> > code is
> > > > not currently executed, since Class.newInstance is not implemented
> > in
> > > > Java.
> > > >
> > > > WBR,
> > > >     Pavel.
> > > > On 3/21/07, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> > > >
> > > > > 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
> > > > > >
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > > Pavel Pervov,
> > > > Intel Enterprise Solutions Software Division
> > > >
> > >
> > >
> > >
> > > --
> > > Pavel Pervov,
> > > Intel Enterprise Solutions Software Division
> > >
> >
>
>
>
> --
> Pavel Pervov,
> Intel Enterprise Solutions Software Division
>



-- 
Pavel Pervov,
Intel Enterprise Solutions Software Division

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