G1gc compaction algorithm

[Martin Makundi]

Our  XX:G1HeapWastePercent  is 1%

**
Martin


2014-07-16 10:25 GMT+03:00 yao <yaoshengzhe at gmail.com>:

> Hi Martin,
>
> I think you may mean do a normal GC when you say "compacting",  then
> that's exactly what this JIRA talk about. If you really mean do a cross
> region compacting (combing live objects from several regions to a single
> one), I don't think this is implemented so far, at least in jvm 7. Even
> that was implemented, if your heap has free regions, I think compacting
> doesn't really matter. In addition, there are several G1 parameters you can
> tune to prevent scattered regions (regions with few live objects), see
> http://www.oracle.com/technetwork/articles/java/g1gc-1984535.html.
> Without seeing the full gc log, I cannot say much how to tune G1 for your
> case but I would definitely try reducing XX:G1HeapWastePercent first.
>
> Best
> Shengzhe
>
>
> On Wed, Jul 16, 2014 at 12:11 AM, Martin Makundi <
> martin.makundi at koodaripalvelut.com> wrote:
>
>>
>>> On Wed, 2014-07-16 at 10:02 +0300, Martin Makundi wrote:
>>> > > > +PrintHeapAtGC -XX:+PrintHeapAtGCExtended .
>>> >
>>> > Does it print only on Full GC or any GC? Any gc might be an overkill.
>>>
>>> Unfortunately any GC :/
>>>
>>> >
>>> > >  You want that probably:
>>> > > https://bugs.openjdk.java.net/browse/JDK-8038487
>>> >
>>> > I cannot comment (didn't find a way to register as user) on that entry
>>> > but you could add a comment on my behalf that   "continuous parallel
>>> > compaction"  would be nice.
>>>
>>> I can add a comment, but what do you mean with "continuous parallel
>>> compaction" if I may ask, and what exact purpose does it serve?
>>>
>>> The terms are too generic to me to discern any particular functionality.
>>>
>>
>> I mean that currently compacting occurs on full gc meaning
>> stop-the-world. Would be nice if compacting would occur in parallel while
>> app is running and taking into account all timing targets such as
>> MaxGCPauseMillis etc.
>>
>> **
>> Martin
>>
>>>
>>> Thanks,
>>>   Thomas
>>>
>>>
>>>
>>
>> _______________________________________________
>> hotspot-gc-use mailing list
>> hotspot-gc-use at openjdk.java.net
>> http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.openjdk.java.net/pipermail/hotspot-gc-use/attachments/20140716/34e3732f/attachment-0001.html>