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From "Mikhail Fursov" <mike.fur...@gmail.com>
Subject Re: [DRLVM][JIT] write barrier broken by new jit opts?
Date Thu, 11 Jan 2007 11:35:54 GMT
On 11 Jan 2007 17:26:13 +0600, Egor Pasko <egor.pasko@gmail.com> wrote:
> On the 0x25B day of Apache Harmony Mikhail Fursov wrote:
> > IMO disabling GC for inlined arraycopy IR region is a good idea and it
> > should work.
> > Other proposals from me here:
> > 1) Why to report each object separately? May be calling wb helper once
> with
> > array of objects could be better?
> AFAIR, Robin proposed to report array updates by chunks, which is a
> good idea for fast thread suspension. WB once for small arrays, wb
> several times for large arrays.

The issues that I did not understand from Robin's post are:
1) Why do we need chunks?
2) What does object_write_barrier(dest) report in algorithm with chunks?

> 2) Another solution could be if GC will provide a helper written with
> > vmmagic for array copying by itself?
> yes, that makes it a) more elegant/supportable than JIT magic b) has
> GC specifics in GC. But on the other hand we should limit this vmmagic
> functionality by the "optimized" part of arraycopy. All other
> exception throwing pecularities are more natural to implement on JIT
> or VM side.

Dividing arraycopy  into different parts implies additional layer in GC-JIT
communication in this case. I see no reasons why not to do nullpointer or
bounds check in vmmagic helper.

> Egor Pasko

Mikhail Fursov

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