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

[Matthias Baesken]

On Fri, 5 Apr 2024 22:47:55 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

> I don't have strong opinion if it's good to have default file path for `jcmd GC.heap_dump`, just some thoughts. We have several ways to heap dump:
> 
> 1. `-XX:+HeapDumpOnOutOfMemoryError`
> 2. `-XX:+HeapDumpBeforeFullGC`, `-XX:+HeapDumpAfterFullGC`
>    in the case `HeapDumpPath` and `HeapDumpGzipLevel` are used (this is not mentioned in the options' description, need to fix it)

Was that ever a problem raised by users that the OOME and the GC related heap dumps end up at the same location ?


> 3. `jcmd GC.heap_dump`
> 4. `jmap -dump`
>    it uses "dumpheap" Attach operation, implemented by AttachListener directly
> 5. `HotSpotDiagnosticMXBean.dumpHeap()`;
> 
> Current patch looks inconsistent: If HeapDumpPath is used as default, HeapDumpGzipLevel should be used as default too (note that default path has different extension depending on HeapDumpGzipLevel); If (3) has defaults, why (4) and (maybe) (5) don't have the same defaults?

Yes , probably with 1. + 2,  and now (with the patch) 3. using HeapDumpPath the others should use it most likely too.
(but our users just asked for 3. that's why the patch).
About HeapDumpGzipLevel , I could add this (I think this was already mentioned), but before adding it I wanted to be sure that there the change is supported.

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PR Comment: https://git.openjdk.org/jdk/pull/18190#issuecomment-2041981493