Oleksiy Stashok wrote:
> Hi Charlie,
>
>> I haven't had a chance to look in detail at the implementation
>> details of the SlabMemoryManager and how it's used. But, I did
>> notice in the object diagram for Slab, a finalize() method.
>> Depending on how Slab and the classes that inherit Slab are used, we
>> might consider looking into the possibility of migrating to using a
>> "ReferenceQueue" approach to clean things up rather than using
>> finalize().
>>
>> finalize() can be problematic in that it may take several gc events
>> for an object with a finalize() method to get collected.
> I see, currently we override finalize just for statistics reasons (we
> calculate total amount of reclaimed memory). In this case, IMHO, we
> can just make sure, that even if finalize() is called several times
> for single object - we will calculate statistics right way.
>
What I really meant by "finalize() can be problematic in that it may
take several gc events for an object with a finalize() method to get
collected." is that using a finalizer in general is problematic, not
anything specific about what Slab.finalize() was doing as being
problematic. It's the use of a finalizer itself.
In short, any object with a finalize() method will most of the time
require at least 2 gc events to be fully garbaged collected. The first
gc event usually just puts the object on the finalizer queue, the 2nd gc
event will then execute the finalize() method and finish collecting it.
In cases where the finalizer queue depth is deep, the entire queue may
not get cleared in one gc event. In such as case, an object with a
finalize() method may sit on on the finalizer queue for multiple gc
events beyond the first gc event place the object on the finalizer
queue. So, it is possible in some circumstances for an object with a
finalize() method to take more than 2 gc events to be collect, (1 gc
event to get put on the finalizer queue, 1 or more additional gc events
to get pulled off the finalizer queue and be executed).
In short, it's best to avoid using a finalize() method.
Hope that makes more sense?
thanks,
charlie ...
> Thanks.
>
> WBR,
> Alexey.
>
>>
>>
>> charlie ...
>>
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