RFR: Fix TestUnifiedLoggingSwitchStress test failure

[Aleksey Shipilev]

On 06/01/2018 06:42 PM, Zhengyu Gu wrote:
>>> okay: http://cr.openjdk.java.net/~zgu/shenandoah/degen_tq_stats/webrev.01/
>>
>> Looks good.
>>
>> But I still wonder why can't we simplify the whole thing? Remove the TQ stats block from
>> SCM::mark_from_roots() completely, move reset past the print in SCM::finish_mark_from_roots()? Let
>> the queues finish, and print+reset.
>>
>> For example:
>>
>> http://cr.openjdk.java.net/~shade/shenandoah/tq-why/webrev.01/src/hotspot/share/gc/shenandoah/shenandoahConcurrentMark.cpp.sdiff.html
>>
> 
> I can try this, but I suspect it only works with all success cycles.

Please do. I think Degenerated should finish up all queue work in the same
SCM::finish_mark_from_roots, so by the time we are printing, everything should be in order. It makes
little sense trying to print queue stats while there is still work in them.

-Aleksey