RFR: 8219414: SA: jhsdb jsnap throws UnmappedAddressException with core generated by gcore

[Chris Plummer]

[adding runtime]

Hi Yasumasa,

Overall looks good. Just a couple of questions.

Do we have the same footprint concerns with the shared mappings as we 
did with the private mappings? If not, possibly it doesn't need an 
option and should always be enabled.

thanks,

Chris

On 2/20/19 12:03 AM, Yasumasa Suenaga wrote:
> Hi all,
>
> Please review this webrev:
>
>    JBS: https://bugs.openjdk.java.net/browse/JDK-8219414
>    webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8219414/webrev.00/
>
> I tried to get PerfCounter values via `jhsdb jsnap` from core image
> which is generated by `gcore` (provided by GDB), but I encountered
> UnmappedAddressException.
>
> It is caused by `generate-core-file` on GDB regards `coredump_filter` on procfs.
>
>    https://sourceware.org/gdb/onlinedocs/gdb/Core-File-Generation.html
>
> JDK-8200613 introduced `DumpPrivateMappingsInCore` for CDS. I want to
> introduce `DumpSharedMappingsInCore` for shared memory mapping.
>
> Currently `DumpPrivateMappingsInCore` affects when `UseSharedSpaces` is enabled.
> I want `DumpPrivateMappingsInCore` to affect independently in this
> change because file-backed private memory which is not CDS might be
> useful in the future.
>
>
> Thanks,
>
> Yasumasa