Well, the GC is free to delay garbage collection until "out of
memory", so the scenario could be that heap builds up, and as memory
is needed, "trash" is swapped out by the OS as you suggest, until the
-Xmx limit is hit, and the GC will now walk (and compact) the heap,
checking each block if it has been marked or not.

I suspect that many of the tuning parameters affect the behavior, as
well as the exact usage patterns in the code.

I am not suggesting one way over the other, just that your categorical
statement that OS will swap out unused memory isn't that simple.


Cheers
Niclas

On Sun, Dec 4, 2011 at 8:03 PM, Luke Daley <[email protected]> wrote:
>
>
>
>
> On 04/12/2011, at 12:11 AM, Niclas Hedhman <[email protected]> wrote:
>
>> On Sun, Dec 4, 2011 at 6:14 AM, Luke Daley <[email protected]> wrote:
>>> I don't think this is much of an issue. The OS will page out the unused JVM 
>>> heap.
>>
>> Depends on GC settings. Potentially you keep filling up all memory
>> with dead objects, then hit a full GC cycle which may take 'forever'
>> to complete.
>
> I don't quite understand the kind of lifecycle that would trigger this.
>
> Would you mind going into a bit more detail?
>
>
>
>
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-- 
Niclas Hedhman, Software Developer
http://www.qi4j.org - New Energy for Java

I live here; http://tinyurl.com/3xugrbk
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