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From "Xiao-Feng Li" <xiaofeng...@gmail.com>
Subject Re: Comparison of Harmony GC_Gen vs. Parrot
Date Sun, 06 Apr 2008 23:41:53 GMT
Senaka, thanks for the page. I think the most important things are
related to the VM <-> GC protocol. Some questions that may help you:
1. How Parrot layout/encode an object/array? fields, size, object
header info, etc.
2. How Parrot layout/arrange the heap? free list? pages?
3. What's the process of an object creation? When and how?
4. How is a collection process triggered?
5. How does Parrot GC trace live objects and collect them?

Some of the questions above might be GC internals, so it's more
desirable if you can understand the Parrot VM's assumptions on GC.
I.e., does it assume the heap is laid out in certain way, does it
assume the objects are encoded in certain way, does it assume the
roots are enumerated in certain way, etc.? Depending on your progress,
more details might be needed later on.

For this project, you might have to understand the Parrot current
status for the above questions. It helps you and us to identify the
key issues to resolve, and the main efforts to be focused on. For GC
porting over different VMs, it's not like porting an application over
different OSes, because of the implicit assumptions between VM and GC.
I would expect some redesign work required for GC porting, hence you
have to understand the Parrot design in certain depth.


On Mon, Apr 7, 2008 at 4:26 AM, Alexei Fedotov <alexei.fedotov@gmail.com> wrote:
> Good job, Senaka.
>  The general perception was that internal and external GC interfaces
>  were mixed, which maked this document less usable for harmony-gc-5
>  project than it could be. For example, sweeping, marking and
>  reclaiming are internal interfaces while allocation, stack enumeration
>  (please take a look at vm_enumerate_root_set_all_threads) and gc
>  invocation are external interfaces. We should pay more attention to
>  external interfaces for harmony-gc-5 project.
>  Thanks.
>  On Sun, Apr 6, 2008 at 8:35 PM, Senaka Fernando <senakafdo@gmail.com> wrote:
>  >
>  > Hi all,
>  >
>  >  I have almost finished comparing the two interfaces of Harmony and Parrot.
>  >  However, I'm not 100% sure on whether I got everything right, but I believe
>  >  that most of it is. Therefore, it would be really great if you could review
>  >  the wiki page and let me know whether it is correct and precise.
>  >
>  >  Sections marked as TBD are not yet finalized. And, I have omitted some
>  >  instances of where Harmony supports something and Parrot doesn't for
>  >  simplicity.
>  >
>  >  The wiki page is found at [1]
>  >
>  >  [1] http://wiki.apache.org/harmony/gc_comparison/gc_gen_harmony_vs_parrot
>  >
>  >  Regards,
>  >  Senaka
>  >
>  --
>  With best regards,
>  Alexei


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