Incremental garbage collection

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Incremental garbage collection

Alexandre Bergel-4
Hi!

The garbage collection offered by the Pharo VM has two divisions. One  
for young objects, and another for old objects. I was wondering when a  
young object become old? I start to have a pretty good idea for human  
beings, but I am not so sure for Pharo objects.
Is it when the object survives its first garbage collection?

Cheers,
Alexandre

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Re: Incremental garbage collection

Mariano Martinez Peck


On Mon, May 10, 2010 at 5:33 PM, Alexandre Bergel <[hidden email]> wrote:
Hi!

The garbage collection offered by the Pharo VM has two divisions. One for young objects, and another for old objects. I was wondering when a young object become old? I start to have a pretty good idea for human beings, but I am not so sure for Pharo objects.
Is it when the object survives its first garbage collection?


Hi Alexandre. I am still newbie with VM stuff, but as I understood, yes, young objects become old when they survive to thei first incremental GC. Notice the INCREMENTAL GC and not FULL GC.

But I may be wrong...so I will let other to answer properly ;)

I have just looked at the code and I am not sure where that movement happens :(

Cheers

Mariano
 
Cheers,
Alexandre

--
_,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:
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Re: Incremental garbage collection

Igor Stasenko
In reply to this post by Alexandre Bergel-4
On 10 May 2010 18:33, Alexandre Bergel <[hidden email]> wrote:
> Hi!
>
> The garbage collection offered by the Pharo VM has two divisions. One for
> young objects, and another for old objects. I was wondering when a young
> object become old? I start to have a pretty good idea for human beings, but
> I am not so sure for Pharo objects.
> Is it when the object survives its first garbage collection?
>
I'd say, whenever VM decides to change a youngStart pointer.
Its quite sophisticated, and having a lot of quirks & preconditions.
But after compaction (either incremental or full), it usually picks a
free memory region which will serve as a space
for newly created objects. After that, obviously, all objects, which
survived GC treated as old ones.


> Cheers,
> Alexandre
>
> --
> _,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:
> Alexandre Bergel  http://www.bergel.eu
> ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;.
>
>
>
>
>
>
> _______________________________________________
> Pharo-project mailing list
> [hidden email]
> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
>



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Re: Incremental garbage collection

johnmci
http://www.smalltalkconsulting.com/papers/GCPaper/GCTalk%202001.htm

see slides 46 & 47

You need to have a tenure event, or a full GC to move the youngStart pointer
past all previously allocated objects, thus promoting a previously allocated
object from new space into old space.

There is btw a primitive I added many years back
primitiveForceTenure

SystemDictionary>>forceTenure

Understanding when and why you would want to use it is another question...


On 2010-05-10, at 9:02 AM, Igor Stasenko wrote:

> On 10 May 2010 18:33, Alexandre Bergel <[hidden email]> wrote:
>> Hi!
>>
>> The garbage collection offered by the Pharo VM has two divisions. One for
>> young objects, and another for old objects. I was wondering when a young
>> object become old? I start to have a pretty good idea for human beings, but
>> I am not so sure for Pharo objects.
>> Is it when the object survives its first garbage collection?
>>
> I'd say, whenever VM decides to change a youngStart pointer.
> Its quite sophisticated, and having a lot of quirks & preconditions.
> But after compaction (either incremental or full), it usually picks a
> free memory region which will serve as a space
> for newly created objects. After that, obviously, all objects, which
> survived GC treated as old ones.
>
>
>> Cheers,
>> Alexandre
>>
>> --
>> _,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:
>> Alexandre Bergel  http://www.bergel.eu
>> ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;.
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>> Pharo-project mailing list
>> [hidden email]
>> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
>>
>
>
>
> --
> Best regards,
> Igor Stasenko AKA sig.
>
> _______________________________________________
> Pharo-project mailing list
> [hidden email]
> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
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===========================================================================
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Re: Incremental garbage collection

Alexandre Bergel-4
Thanks John, your slides are really good.

Alexandre


On 10 May 2010, at 12:41, John M McIntosh wrote:

> http://www.smalltalkconsulting.com/papers/GCPaper/GCTalk%202001.htm
>
> see slides 46 & 47
>
> You need to have a tenure event, or a full GC to move the youngStart pointer
> past all previously allocated objects, thus promoting a previously allocated
> object from new space into old space.
>
> There is btw a primitive I added many years back
> primitiveForceTenure
>
> SystemDictionary>>forceTenure
>
> Understanding when and why you would want to use it is another question...
>
>
> On 2010-05-10, at 9:02 AM, Igor Stasenko wrote:
>
>> On 10 May 2010 18:33, Alexandre Bergel <[hidden email]> wrote:
>>> Hi!
>>>
>>> The garbage collection offered by the Pharo VM has two divisions. One for
>>> young objects, and another for old objects. I was wondering when a young
>>> object become old? I start to have a pretty good idea for human beings, but
>>> I am not so sure for Pharo objects.
>>> Is it when the object survives its first garbage collection?
>>>
>> I'd say, whenever VM decides to change a youngStart pointer.
>> Its quite sophisticated, and having a lot of quirks & preconditions.
>> But after compaction (either incremental or full), it usually picks a
>> free memory region which will serve as a space
>> for newly created objects. After that, obviously, all objects, which
>> survived GC treated as old ones.
>>
>>
>>> Cheers,
>>> Alexandre
>>>
>>> --
>>> _,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:
>>> Alexandre Bergel  http://www.bergel.eu
>>> ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;.
>>>
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Pharo-project mailing list
>>> [hidden email]
>>> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
>>>
>>
>>
>>
>> --
>> Best regards,
>> Igor Stasenko AKA sig.
>>
>> _______________________________________________
>> Pharo-project mailing list
>> [hidden email]
>> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
>
> --
> ===========================================================================
> John M. McIntosh <[hidden email]>   Twitter:  squeaker68882
> Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com
> ===========================================================================
>
>
>
>
> _______________________________________________
> Pharo-project mailing list
> [hidden email]
> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project


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