RFR: 8252842: Extend jmap to support parallel heap dump

[Chris Plummer]

On Thu, 18 Feb 2021 16:39:46 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> Dear All, 
>>      I am going to create a CSR for the new internal command "dumpheapext", one problem is that seem if a new CSR is created, this PR will depends on 2 CSRs, I am not sure is this reasonable?  Thanks!
>
>>  I am going to create a CSR for the new internal command "dumpheapext", one problem is that seem if a new CSR is created, this PR will depends on 2 CSRs, I am not sure is this reasonable? Thanks!
> 
> I have no idea if you can add two CSRs to a PR and a CR. If you can, then I see no issue with doing that. If not, we might need to talk to the CSR committee to see how best to handle it.

> 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.

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