RFR: Ensure tasks use correct number of workers

[Aleksey Shipilev]

On 09/18/2017 02:42 PM, Zhengyu Gu wrote:
> Ensure that GC tasks follow parallel/concurrent worker protocol, use correct number of worker threads.
> 
> Webrev: http://cr.openjdk.java.net/~zgu/shenandoah/assert_workers/webrev.00/

*) I see that ShenandoahCollectorPolicy computes the number of workers for different phases. Do we
want at least do the call to to policy, instead of using ParallelGCThreads/ConcGCThreads directly?
This will capture all worker count decisions, however static, in one place.

*) How long is TestGCThreadGroups? It seems to be derived from LotsOfCycles test, but we can really
do much smaller allocation target, e.g. 10x lower?

*) Typo "SWT":

 257 void ShenandoahPartialGC::do_partial_collection() {
 258   assert(SafepointSynchronize::is_at_safepoint(), "SWT partial GC");

*) Type "none-regular":

  44   // bypass concurrent/parallel protocol check for none-regular paths, e.g. verifier, etc.

Thanks,
-Aleksey