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

[Jini George]

Your changes look good to me overall, Yasumasa. A couple of points though.

* Since you are making modifications to have DumpPrivateMappingsInCore 
independent of CDS, in os::abort(), you would also need change the 
following lines:
1361 #if INCLUDE_CDS
1362     if (UseSharedSpaces && DumpPrivateMappingsInCore) {
1363       ClassLoader::close_jrt_image();
1364     }
1365 #endif

to

1361
1362     if (DumpPrivateMappingsInCore) {
1363       ClassLoader::close_jrt_image();
1364     }

But this might cause the zero build to fail due to the call to 
ClassLoader::close_jrt_image() 
(https://bugs.openjdk.java.net/browse/JDK-8215342). So, it might be 
better to guard the above lines with #ifndef ZERO to have:

1361 #ifndef ZERO
1362     if (DumpPrivateMappingsInCore) {
1363       ClassLoader::close_jrt_image();
1364     }
1365 #endif


* Also, one nit:

http://cr.openjdk.java.net/~ysuenaga/JDK-8219414/webrev.00/src/hotspot/os/linux/os_linux.cpp.html

- Could you please remove or modify the comment at line 3436 since 
set_coredump_filter() is not restricted to include only largepages now?

Thank you!
Jini.


On 2/21/2019 7:43 AM, Yasumasa Suenaga wrote:
> Thanks Chris!
> 
> 
> Yasumasa
> 
> 
> 2019年2月21日(木) 11:08 Chris Plummer <chris.plummer at oracle.com 
> <mailto:chris.plummer at oracle.com>>:
> 
>     Ok. The changes look fine to me then.
> 
>     thanks,
> 
>     Chris
> 
>     On 2/20/19 6:02 PM, Yasumasa Suenaga wrote:
>      > Hi Chris,
>      >
>      > I grep'ed with "MAP_SHARED" on jdk/src.
>      > Shared memory is used in ZGC (ZBackingFile and
>     ZPhysicalMemoryBacking)
>      > and in FileChannel::map at least.
>      >
>      > I think we have memory footprint concern about them, but shared
>     memory
>      > should be dumped.
>      > If we did not get them, we cannot analyze ZGC related behavior and
>      > other code which uses shared memory.
>      > (We can pass FD to os::reserve_memory - it will use shared memory if
>      > FD is passed.)
>      >
>      > Thus I want to introduce `DumpSharedMappingsInCore` for dumping
>     shared
>      > memory and set it to true by default.
>      >
>      >
>      > Thanks,
>      >
>      > Yasumasa
>      >
>      >
>      > 2019年2月21日(木) 3:10 Chris Plummer <chris.plummer at oracle.com
>     <mailto:chris.plummer at oracle.com>>:
>      >> [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
>      >>
> 
>