RFR: 8252842: Extend jmap to support parallel heap dump

[Lin Zang]

On Fri, 19 Feb 2021 04:20:14 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

> > CSR requests are associated with a JBS issue not a PR. If there exists a CSR request for this JBS issue and you are making further changes then move the CSR back to draft and update it and re-submit it.
> > Thanks,
> > David
> 
> The complexity comes from the fact there there are really two separate features to call out. One is adding the `parallel=<n>` option to `jmap -dump`, and the other is adding the `dumpheapext` command to the attach api. However, they are not really separable since `dumpheapext` is needed in order to support `parallel=<n>`. We could lump them into one CR and CSR, but it seems this is overloading them a bit. I guess the other option is to try to separate the `dumpeheapext` part and do that first, although it really would serve no purpose until `parallel=<n>` is added.

Hi Chris and David, 

I guess we can create a sub-task of dumpheapext, I have created one(https://bugs.openjdk.java.net/browse/JDK-8261943) and then create a CSR related with it. 
Then we have two CSRs, one for introducing "parallel=" option and one for "dumpheapext" command. And both are fixed in this PR. 
What do you think?

Thanks, 
Lin

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PR: https://git.openjdk.java.net/jdk/pull/2261