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From Egor Pasko <egor.pa...@gmail.com>
Subject Re: [drlvm] Class unloading support
Date Thu, 26 Oct 2006 12:34:04 GMT
On the 0x20E day of Apache Harmony Pavel Pervov wrote:
> > The  Alexey's solution does not affect devirtualizer at all.
> >
> > How can we do without devirtualizer changes here? We need to replace
> > Object->Vtable with Object->class->vtable. Am I missing something?
> 
> 
> If vtables are pinned Aleksey's solution does not affect JITs at all.
> 
> If vtables move, it will be one more level of indirection for guarded
> devirtualization: was object->vtable, will be object->vtable->class.

yeah, that is why unpinning them might appear a perf-boost as well as
slowdown. I cannot find any solution not to slow down here. (thinking
of obj->class->vtable which is bad for virtual calls, keeping both
obj->vtable->class and obj->class->vtable is bad for footprint) Is it
really the problem each JVM designer meets? :)

> Unpinning vtables does not cause the need to enumerate them from JIT, if JIT
> does not store pointers to them.

yes, as well as all other objects

-- 
Egor Pasko, Intel Managed Runtime Division


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