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

[Yasumasa Suenaga]

Thanks Chris!


Yasumasa


2019年2月21日(木) 11:08 Chris Plummer <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>:
> >> [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
> >>
>
>
>
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