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From "Mikhail Fursov" <mike.fur...@gmail.com>
Subject Re: Re: [rant] Memory options in VM -- why is the default not 'unlimited'
Date Sun, 30 Jul 2006 18:50:08 GMT
On 7/31/06, Santiago Gala <sgala@apache.org> wrote:
>
> El dom, 30-07-2006 a las 00:16 +0100, Alex Blewitt escribió:
>
> (...)
>
> > However, if the GC is generational, why does it need to be contiguous?
>
> Some (most?) implementations of write barriers for generational GC
> assume that all old memory is below or above all nurseries, so that the
> old->new test can be done with a simple address comparison.
>
> So, while they are not fully contiguous, they make some assumptions on
> memory layout, even if it is just for efficiency.
>
> Testing if a pointer is inside any of a number of memory areas for each
> assignment is a fairly expensive operation.
>

Extra bit/byte in object header can solve this problem..


-- 
Mikhail Fursov

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