[Vm-dev] Explanation of GC behaviour

Bert Freudenberg bert at freudenbergs.de
Fri Jul 5 17:41:06 UTC 2019

A lot of this changed with the introduction of Spur. See
and then come back with more questions ;)

- Bert -

On Fri 5. Jul 2019 at 00:17, Norbert Hartl <norbert at hartl.name> wrote:

> I’m trying to understand better how the GC works because I cannot derive
> that from the parameters in the VirtualMachine object in the pharo image.
> Can someone sketch the position lifecycle of an object or point me to a
> document where this is described? Maybe the following questions help in
> helping.
> - object allocation happens in eden space?
> - after a few cycles eden space objects are considered survivor. Which is
> the process for a cycle? incremental GC run?
> - survivors are moved to youngSpace? After how many cycles?
> - after a few more cycles an object is moved to old space?
> - the term tenuring describes the process of moving object from young
> space to old space or also from eden to young space?
> - when is a full GC triggered?
> - a full GC is the only process that removes objects from old space?
> - the size of eden space and young space are fixed or relative to heap
> size?
> - how big is the initial size of old space when the vm is started?
> - if the heap size is not restricted is it likely a full GC happens or
> does the heap grow indefinite?
> - what does the VirtualMachine>>#tenureCount mean? Is the tenuring runs or
> tenured objects?
> Before the list gets to long I stop here. Your answers might remove many
> of them already.
> thanks in advance,
> Norbert

Dr. Bert Freudenberg
7275 Franklin Avenue #210
Los Angeles CA 90046
+1 (818) 482-3991
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