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From "Caldarale, Charles R" <Chuck.Caldar...@unisys.com>
Subject Re: Setting the Right Amount of Memory
Date Sun, 20 Jun 2010 15:01:38 GMT
On Jun 20, 2010, at 4:24, "André Warnier" <aw@ice-sa.com> wrote:

>> The time it takes to perform a GC is *not* dependent on the number or
>> size of dead objects, just on the live ones.
>
> That is counter-intuitive.  Pray, why is that ?

All modern GC algorithms are variations of mark-sweep-compact.  The  
basic operation consists of following the object reference graph from  
a set of known roots (eg, thread stack frames), marking each  
discovered object with a found flag, and copying the found objects to  
an unoccupied area.  Unreachable (dead) objects are never encountered,  
so their number or size does not come into play.  The space occupied  
by dead objects is automatically reclaimed as live objects are copied  
over them.

There are links to various papers and descriptions on the Java  
technologies page:

http://java.sun.com/javase/technologies/hotspot/gc-index.jsp

Googling for mark-sweep-compact will get you some of the academic  
papers and continuing research into the topic.

- Chuck

(Now in a hotel watching the All Whites vs the Azzurri.)

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