RFR 8204947: Port ShenandoahTaskTerminator to mainline and make it default

Zhengyu Gu zgu at redhat.com
Thu Nov 29 01:21:23 UTC 2018


Hi Roman,

On 11/28/18 3:45 PM, Roman Kennke wrote:
> I believe if you add a flag, you need to file a CSR.

Thanks for reminding me, just filed CSR.

-Zhengyu

> 
> Will have a deeper look at the patch later..
> 
> Thanks,
> Roman
> 
> 
>> Hi,
>>
>> ShenandoahTaskTerminator is based on Google's work stealing protocol,
>> described in paper [1]. The implementation diverges in a way to
>> emphasize termination latency vs. power efficiency (see comments in code
>> for details).
>>
>> Shenandoah switched to ShenandoahTaskTerminator as default terminator,
>> shortly after it was implemented, and has been very stable since.
>>
>> On performance side, it showed better termination latency on almost all
>> tests/benchmarks I ran, comparing to ParallelTaskTerminator. As the
>> result, we (Shenandoah) purged fallback branches and uses it as the sole
>> task terminator.
>>
>> This patch introduces a new experimental flag "UseOWSTTaskTerminator"
>> (default: true), and switches G1 and Parallel GC to use it as default
>> terminator. You can switch back to ParallelTaskTerminator with JVM
>> option "-XX:+UnlockExperimentalVMOptions -XX:-UseOWSTTaskTerminator"
>>
>> I did not port it to CMS, as it is depreciated.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8204947
>> Webrev: http://cr.openjdk.java.net/~zgu/JDK-8204947/webrev.00/
>>
>> Test:
>>    hotspot_gc and vmTestbase_vm_gc on Linux 64.
>>
>>
>> [1] Understanding and improving JVM GC work stealing at the data center
>> scale (http://dl.acm.org/citation.cfm?id=2926706)
>>
>> Thanks,
>>
>> -Zhengyu
> 


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