RFR(XS): 8198510: Limit GC threads for small Java heap

[Doerr, Martin]

Hi,

the VM currently starts a large amount of GC threads on systems with many CPUs regardless of the Java heap size.
This doesn't make sense for very small heap sizes.

The number of ParallelGCThreads can be observed by e.g.:
jdk/bin/java -Xmx128m -XX:+PrintFlagsFinal -version|grep GCThreads

My proposal is to use up to 1 GC thread per 64 MB of heap:
http://cr.openjdk.java.net/~mdoerr/8198510_gc_threads/webrev.00/

Please review.

Best regards,
Martin

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