[Vm-dev] Re: [Pharo-dev] blog post

[Florin Mateoc]

Hi Eliot,


> Eliot Miranda <eliot.miranda at gmail.com <http://lists.squeakfoundation.org/mailman/listinfo/vm-dev>> wrote:
>
> Hi Stéph,
>
> On Fri, Sep 6, 2013 at 9:35 AM, Stéphane Ducasse
> <stephane.ducasse at inria.fr <http://lists.squeakfoundation.org/mailman/listinfo/vm-dev>>wrote:
>
>/ Hi eliot
/>>/
/>/> This is really good that you write this blog. I read and I saw ephemerons
/>/> (excellent because we were discussing them again today with esteban and
/>/> igor)
/>/> I have some questions that may be are stupid.
/>/>         - I was wondering if you plan to have a dedicated class space.
/>/> Clement told me that in Chrome (but I may be wrong) they have that and in
/>/> the class space the classes are not moved. But with the table you are sure
/>/> that your index do not change so may be the gain is not important.
/>>/
/>
> exactly.


Wouldn't a fixed, dedicated, class space facilitate though sharing between multiple images?
This was a nice feature in VW, and I think it may become even more important with the trend towards multi-core.

I also assume that a dedicated space for pinned memory might also simplify the garbage collector and even help performance a bit.

To me it appears that this kind of specialization of memory (splitting it into dedicated spaces) would almost always be a win.
While it increases the complexity by increasing the number of components to manage, it also simplifies the components, since they need to handle fewer special cases.
But I have never implemented a vm :)

I am also curious if you are including immediate floats in your 64-bit object format.
I am sure you know about it, but I saw this nice article about tagging in the current JavaScript implementations:
http://wingolog.org/archives/2011/05/18/value-representation-in-javascript-implementations

You only mentioned in your blog tagging for the 32-bit world (I think).
Can you please add some comments about 64-bit tagging?

Regards,
Florin

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