RFR: JDK-8261034: improve jcmd GC.class_histogram to support parallel

[Chris Plummer]

On Sat, 13 Feb 2021 05:05:48 GMT, Lin Zang <lzang at openjdk.org> wrote:

> Yes, It is not known at present, but the heapInspect and heapDumper accept an outputStream, and the actual parallel thread number can be got by gang->active_workers() after WithUpdatedActiveWorkers. Then maybe some code can be added there to record the actual number and finally print to outputStream at the end.

So you are proposing having the attach "heapdumpext" and "inspectheap" commands always print the number of threads used? I'm not so sure that is a good idea since there are probably existing tools and tests that parse the output, and changing its format could break them.

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PR: https://git.openjdk.java.net/jdk/pull/2379