Depth first object copying for all GC?
jon.masamitsu at oracle.com
Thu May 7 00:23:19 UTC 2015
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
ParallelGC used to have such an option. It made the code harder to
as far as I can recall, there was very little use of the option. We
it. I recall maybe 1 complaint about it.
> https://bugs.openjdk.java.net/browse/JDK-6450584: Improve object
> copying order in parallel scavenge
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