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

[Jini George]

Looks good to me, Yasumasa. Thanks!

-Jini.

On 2/21/2019 11:45 AM, Yasumasa Suenaga wrote:
> Hi Jini,
> 
> Thank you for your comment.
> 
> I uploaded new webrev.
> Could you review again?
> 
>    http://cr.openjdk.java.net/~ysuenaga/JDK-8219414/webrev.01/
> 
> diff from webrev.00 is here:
>    http://hg.openjdk.java.net/jdk/submit/rev/bb58c9d41381
> 
> 
> Thanks,
> 
> Yasumasa
> 
> 
> 2019年2月21日(木) 12:30 Jini George <jini.george at oracle.com>:
>>
>> 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
>>>       >>
>>>
>>>