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From "Weldon Washburn" <weldon...@gmail.com>
Subject Re: [DRLVM] GC/VM interface discussion
Date Wed, 12 Jul 2006 05:17:26 GMT
On 7/11/06, Robin Garner <robin.garner@anu.edu.au> wrote:
> Salikh Zakirov wrote:
> > Ivan Volosyuk wrote:
> >
> >> My idea here, is if the function is required by VM, it can be emulated
> >> on VM side via "alloc + pin". Of cause, it is not the same as
> >> gc_pinned_alloc. The behaviour of GC will be suboptimal in that case.
> >>
> >
> > In fact, gc_alloc_pinned() is not intended to be equivalent to gc_alloc()
> > followed by gc_pin() for the following reasons
> >
> > 1) gc_pin() is optional operation, and may be absent in simplest collectors
> > 2) gc_pin() is not required to succeed, and the GC may decide to reject
> >    object pinning (e.g. based on some memory footprint/performance compromise).
> >    The success of operation must be checked by using gc_is_object_pinned()
> > 3) gc_alloc_pinned() may be implemented in a much more efficient way than
> >    pinning of arbitrary object, e.g. by introducing the separate fixed space
> >    with size-segregated lists or other malloc-like management algorithms.
> >
> >
> Perhaps a more relevant discussion is exactly what
> hints/suggestions/requirements the VM and MM give each other on an
> allocation request.  MMTk allows the VM to explicitly request allocation
> in a specific space, and this can/has been used to implement
> optimizations such as pre-tenuring.

Yes!  I like it :)

> IMO a good high-performance
> interface should at least allow the VM to provide a variety of hints to
> the MM.

Yes!  I hope you can help us define these performance hint APIs.

>
> -- Robin
>
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>


-- 
Weldon Washburn
Intel Middleware Products Division

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