Depth first object copying for all GC?

Srinivas Ramakrishna ysr1729 at gmail.com
Sat May 9 02:21:41 UTC 2015



ysr1729

> On May 7, 2015, at 12:25, Jon Masamitsu <jon.masamitsu at oracle.com> wrote:
> 
> Ramki,
> 
> Did you ever make ParNew depth-first copying?
> 

No, I didn't ever get around to it, as far as I recall... 

-- ramki

> Jon
> 
>> On 05/07/2015 11:51 AM, Jon Masamitsu wrote:
>> 
>> 
>>> On 05/06/2015 07:56 PM, Tangwei (Euler Architecture & Design Dept) wrote:
>>> Would you help to list the object copying policy for different GC?  Or pointing out where to find such information? 
>> 
>> For the most part UseParallelGC and UseG1GC has depth-first copying.  UseConcMarkSweepGC 
>> and UseSerialGC use breadth-first.  I qualify that because I've heard people argue about whether
>> that's 100% true.
>> 
>> Jon
>> 
>>>  
>>> Regards!
>>> wei
>>>  
>>> From: hotspot-gc-dev [mailto:hotspot-gc-dev-bounces at openjdk.java.net] On Behalf Of Jon Masamitsu
>>> Sent: Thursday, May 07, 2015 8:23 AM
>>> To: hotspot-gc-dev at openjdk.java.net
>>> Subject: Re: Depth first object copying for all GC?
>>>  
>>>  
>>> 
>>> On 5/6/2015 4:34 AM, Tangwei (Euler Architecture & Design Dept) wrote:
>>> Hi All,
>>>   As a newbie in GC, I found some discussion on object copying order in following slides: breadth vs. depth.
>>> It mentioned that “Any static policy will hurt some applications and help others”. After searching, there is a BZ shows
>>> the object copying order has been switched from breadth to depth for ParallelGC in OpenJDK, please correct if I am wrong.
>>> Anyone can help to confirm if all GC in OpenJDK use depth first copying now?
>>> 
>>> No, not all the GC's use depth first copying.
>>> 
>>> 
>>> Is there any performance consideration to choose depth first instead of controlling by option?
>>> 
>>> Yes, there is a performance cost to optionally using depth-first or breadth-first.
>>> ParallelGC used to have such an option.  It made the code harder to maintain and,
>>> as far as I can recall, there was very little use of the option.  We removed the
>>> it.  I recall maybe 1 complaint about it.
>>> 
>>> Jon
>>> 
>>> 
>>>  
>>> http://www.oracle.com/technetwork/server-storage/ts-6434-159339.pdf
>>>  
>>>  
>>> https://bugs.openjdk.java.net/browse/JDK-6450584: Improve object copying order in parallel scavenge
>>>  
>>>  
>>> Regards!
>>> wei
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/attachments/20150508/fdb4893c/attachment-0001.html>


More information about the hotspot-gc-dev mailing list