RFR (S): 8078669: G1 applies SurvivorAlignmentInBytes to both survivor and old gen

Jon Masamitsu jon.masamitsu at oracle.com
Wed May 20 02:08:54 UTC 2015

On 5/18/2015 2:01 AM, Thomas Schatzl wrote:
> Hi Jon,
> On Wed, 2015-05-13 at 14:15 -0700, Jon Masamitsu wrote:
>> On 5/13/2015 7:33 AM, Thomas Schatzl wrote:
>>> Hi all,
>>>     can I have reviews for the following small fix: since JDK-8060025
>>> survivor alignment has been applied to both survivor and old gen regions
>>> (if enabled of course).
>>> This has gone unnoticed, because the tests somehow detected that in this
>>> situation everyhing is fine due to "someone else that allocated
>>> objects".
>>> The change fixes the problem (in g1Allocator.hpp), and removes this
>> The CR suggests that this change in g1Allocator.hpp is a workaround while
>> waiting for a better fix.  Still true?
> Initially I thought that this change would have noticable performance
> impact. Perf testing showed that this is not the case. Since the
> alternative I could come up with was basically replicating lots of code
> using templates (one variant supporting survivor alignment, the other
> not), I thought that since there is no perf impact, this solution would
> be fine.


Consider the fix Reviewed.

>> The change looks correct as a fix for the specific problem.
>> I'll let you discuss the tests with Dmitry.
> Thanks,
>    Thomas

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