RFR: JDK-8327769: jcmd GC.heap_dump without options should write to location given by -XX:HeapDumpPath, if set [v10]

[Chris Plummer]

On Wed, 10 Apr 2024 13:03:40 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> > One other thing I just realized is that if we go through with this change, then we can't in the future change VM.heap_dump so it can be used without any filename (make it use a default filename when no filename is specified). Setting HeapDumpPath would override this default filename, and it would be really confusing to the user when suddenly heap dumps are not appearing in the default location with the default name because someone decided to specify HeapDumpPath when launching the JVM.
> 
> Isn't this the case already for the -XX:+HeapDumpBeforeFullGC, -XX:+HeapDumpAfterFullGC scenarios? But probably it should be decided first if such a default is planned for VM.heap_dump .

I don't think so, but maybe I'm misunderstanding your point. It may be desirable to have VM.heap_dump support not specifying a filename and instead just have it choose a default name and path, probably the current working directory with a name something like java_pid<pid>.hprof. However, having this default and also using HeapDumpPath if set conflict with each other. Someone could be relying on the VM.heap_dump default, and then suddenly that default is no longer honored because HeapDumpPath was added to the command line. I don't see -XX:+HeapDumpBeforeFullGC or -XX:+HeapDumpAfterFullGC playing a roll in this scenario.

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PR Comment: https://git.openjdk.org/jdk/pull/18190#issuecomment-2048132997