JEP 132: More-prompt finalization

Dmitry Samersoff Dmitry.Samersoff at
Tue Dec 27 12:19:53 PST 2011


It's not a real (escalated) case. Just an accumulation of
what I heard from cu during last five years.

On 2011-12-27 20:49, Jon Masamitsu wrote:

> Before I try to answer your question, do you ever try to use
> System.gc() to get finalizers to run?

Nope. Because (as you write it below) it's too disruptive especially
because I have to call System.gc() twice to dry finalization queue.

>   If you don't because
> System.gc() it too disruptive (generally being stop-the-world),
> are you using CMS and have you tried using System.gc()
> with -XX:+ExplicitGCInvokesConcurrent?

Nope also. In most cases System.gc(CMS) cause valuable performance
degradation for cu's app.

To clarify cu requirements:

e.g Huge trader like CBOE.  It has the application that have to be very
responsive during a stock work day.
   So they tune VM to have no GC during work day. Then they kill the app
and start everything again next morning.

The problem is -  they rely to finalization to do some task. Most
important (but not the only one) one is socket reclaiming .


> Jon
> On 12/24/2011 4:33 AM, Dmitry Samersoff wrote:
>> Jon,
>> One of problem with finalization nowdays is that with 1 Tb heap GC (and
>> thus finalization) never happens.
>> Do you plan to address this problem?
>> -Dmitry
>> On 2011-12-23 20:13, Jon Masamitsu wrote:
>>> David,
>>>  From the VM side there are two issues that I think we should understand
>>> better before we work on an API.  Those are described in the JEP as
>>> 1) more aggressive management of the of finalization queue and 2)
>>> multiple
>>> finalizer threads.  We should see how much of the problem can be
>>> alleviated by either or both or by other VM side changes that occur
>>> to us
>>> during the work and then think about what is left and what information
>>> we want from the user to address what's left.   As Mark has said, I
>>> think there will be a library side JEP at some point for those
>>> discussions.
>>> Jon
>>> On 12/22/2011 6:15 PM, David Holmes wrote:
>>>> On 23/12/2011 9:05 AM, mark.reinhold at wrote:
>>>>> Posted:
>>>> hotspot-dev seems the wrong mailing list to discuss this. It is
>>>> primarily a Java level API. I would suggest using core-libs-dev.
>>>> David

Dmitry Samersoff
Java Hotspot development team, SPB04
* There will come soft rains ...

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