RFR(XXS): 8006894: G1: Number of marking threads missing from PrintFlagsFinal output

[John Cuthbertson]

Hi All,

Can I have a couple of volunteers look over this small change? The 
webrev can be found at: http://cr.openjdk.java.net/~johnc/8006894/webrev.0/

Summary:
When G1 calculates the number of marking threads based upon (the 
develop-only) G1MarkingOverheadPercent or (more usually) 
ParallelGCThreads, we weren't setting the value of ConcGCThreads. As a 
result the output of PrintFlagsFinal would always show a zero if 
ConcGCThreads wasn't specified on the command line:

     uintx ConcGCThreads                             = 0               
{product}

This made it difficult for the performance team to analyze marking 
behavior and offer advice. With this change we now get the calculated 
number of marking threads:

Using ParallelGCThreads (default: 4):

     uintx ConcGCThreads                            := 1               
{product}

Using G1MarkingOverheadPercent (50):

     uintx ConcGCThreads                            := 2               
{product}

Testing:
Command line testing; specjvm98 and dacapo with a low IHOP value 
(marking threshold).

Thanks,

JohnC