RFR (XS): JDK-8047976: Ergonomics for GC thread counts should update the flags

[Bengt Rutisson]

Hi all,

Here's an updated webrev from Sangheon:

http://cr.openjdk.java.net/~brutisso/8047976/webrev.02/

 From Sangheon:

"This includes Thomas's comments about:
1) Moving value set to Arguments::set_g1_gc_flags()
2) Adding jtreg test for G1ConcRefinementThreads variable"

Thanks,
Bengt


On 2014-09-25 11:01, Thomas Schatzl wrote:
> Hi,
>
> On Thu, 2014-09-25 at 09:32 +0200, Thomas Schatzl wrote:
>> Hi,
>>
>> On Wed, 2014-09-24 at 08:51 -0700, Sangheon Kim wrote:
>>> Hi all,
>>>
>>> can I have reviews for the following small change to update
>>> G1ConcRefinementThreads variable?
>>> And also I need a sponsor for this.
>>>
>>> CR:
>>> https://bugs.openjdk.java.net/browse/JDK-8047976
>>>
>>> Webrev:
>>> http://cr.openjdk.java.net/~brutisso/8047976/webrev.00/
>>> <http://cr.openjdk.java.net/%7Ebrutisso/8047976/webrev.00/>
>> Please update the flag during argument processing, not every time the
>> method is called.
>>
>> Somewhere in Arguments::set_g1_gc_flags() would be appropriate I think.
>>
> Please also add a jtreg test case. At least one test case that verifies
> that with G1 the G1ConcRefinementThreads is not zero if nothing or zero
> is passed, and another one that checks that the value passed is taken
> over.
>
> The test could parse the output of -XX:+PrintFlagsFinal. The test
> gc/arguments/TestObjectTenuringFlags.java shows how this is done.
>
> There is also some behavior that seems to be wrong: if you manually set
> the number of G1ConcRefinementThreads to zero (which means
> "automatically select"), -XX:+PrintFlagsFinal still prints
> "G1ConcRefinementThreads := 0". Imo even in this case the output should
> contain the actual number of threads used.
>
> At least if you set ConcGCThreads manually to 0, the flag is set to the
> actual value after argument processing.
>
> ParallelGCThreads also shows 0 here, but I think this part of bug
> JDK-6979279 and should be fixed there.
>
> Thanks,
>    Thomas
>
>