Hi Alexandre,

On Mon, Nov 25, 2013 at 7:42 AM, Alexandre Bergel <alexandre.bergel@me.com> wrote:

Hi Eliot,

I have a question still on segmented memory.

Consider an object �c := OrderedCollection new�. It is likely that the internal "array� and the object c will be in the same generation and in the same memory segment.

There is no guarantee but it is very likely they will end up in the same segment, yes.

�

If I add, let�s say, 30 000 000 elements into c. After the addition the array will be very very big. Which means that it may be in a different segment memory than the one that contains �c�. Do you feel this may be a problem? I am thinking about a long jump between c and array. Long jumps cost more than short jumps right?

I don't think it'll be an issue because statistically it'll affect a minority of collections. �No, its not necessarily the case that there may be a higher cost. �This depends on how the processor's memory hierarchy works. �Further, performance may be more affected by how clustered the elements of the collection are than the collection itself.

Do you feel there are some suboptimal situation with this situation?

I think it's way too early to worry about this kind of thing. �The system needs to work and be tuned. �There's plenty of time to address clustering, etc.

�

Alexandre

NB: I cc the mailing list to see whether other may help in understand better what�s going on with segment and generations
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Alexandre Bergel �http://www.bergel.eu
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On Nov 19, 2013, at 1:37 PM, Eliot Miranda <eliot.miranda@gmail.com> wrote:

> Hi Alexandre,
>
>
> On Mon, Nov 18, 2013 at 7:40 AM, Alexandre Bergel <alexandre.bergel@me.com> wrote:
> Hi Eliot,
>
> Stef told me you are working hard on improving the Pharo VM.
> In particular making the VM support fragmented memory. If I understand correctly, this will relieve the VM from having a continuous block of memory to hold the whole image. Really cool!
>
> A better term is segmented memory. �fragmentation in memory management means free space getting divided into too small pieces to be useful.
>
> I have a general question regarding VM. Are you aware of other Virtual machines supporting this? Does the Java VM support fragmented memory? .Net? V8?
>
> Any VM that uses the train algorithm supports segmented memory. �Any VM that uses "pools" or "regions" uses segmented memory. �VisualWorks' VM supports segments. �I'm pretty sure that V8 .Net & HotSpot provide segmented memory.
>
>
> I would like to mention this in a research paper I am working on.
>
> Cheers,
> Alexandre
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> Alexandre Bergel �http://www.bergel.eu
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> --
> best,
> Eliot

--
best,

Eliot