RFR(M): 8204965: Fix '--disable-cds' and disable CDS on AIX by default (original) (raw)

David Holmes david.holmes at oracle.com
Tue Jun 19 04:54:25 UTC 2018

Hi Volker,

v3 looks much cleaner - thanks.

But AFAICS the change to jvmtiEnv.cpp is also not needed. ClassLoaderExt::append_boot_classpath exists regardless of INCLUDE_CDS but operates differently (just calling ClassLoader::add_to_boot_append_entries).

Thanks, David

On 19/06/2018 2:04 AM, Volker Simonis wrote:

On Mon, Jun 18, 2018 at 8:17 AM, David Holmes <david.holmes at oracle.com> wrote:

Hi Volker,

src/hotspot/share/runtime/globals.hpp This change should not be needed! We do minimal VM builds without CDS and we don't have to touch the UseSharedSpaces defaults (unless recent change have broken this - in which case that needs to be addressed in its own right!) Yes, you're right, CDSONLY/NOTCDS isn't really required here, because UseSharedSpaces is reseted later on at the end of Arguments::parse(). I just thought it would be cleaner to disable it statically, if the VM doesn't support it. But anyway I don't really mind and I've reverted that change in globals.hpp. src/hotspot/share/classfile/javaClasses.cpp AFAICS you should be using INCLUDECDS in the ifdefs not INCLUDECDSJAVAHEAP. But again I'm unclear (as was Thomas) why this should be needed as we have not needed it before. As Thomas notes we have: ./hotspot/share/memory/metaspaceShared.hpp: static bool isarchiveobject(oop p) NOTCDSJAVAHEAPRETURN(false); ./hotspot/share/classfile/stringTable.hpp: static oop createarchivedstring(oop s, Thread* THREAD) NOTCDSJAVAHEAPRETURN(NULL); so these methods should be defined when CDS is not available. Thomas and you are right. Must have been a mis-configuration on AIX where I saw undefined symbols at link time. I've removed the ifdefs from javaClasses.cpp now. Finally, I've also wrapped all the FileMapInfo fields in vmStructs.cpp into CDSONLY macros as suggested by Jiangli because the really only make sense for a CDS-enabled VM. Here's the new webrev: http://cr.openjdk.java.net/~simonis/webrevs/2018/8204965.v3/ Please let me know if you think there's still something missing. Regards, Volker ?? Thanks, David -----

On 15/06/2018 12:26 AM, Volker Simonis wrote: Hi, can I please have a review for the following fix: http://cr.openjdk.java.net/~simonis/webrevs/2018/8204965/ https://bugs.openjdk.java.net/browse/JDK-8204965 CDS does currently not work on AIX because of the way how we reserve/commit memory on AIX. The problem is that we're using a combination of shmat/mmap depending on the page size and the size of the memory chunk to reserve. This makes it impossible to reliably reserve the memory for the CDS archive and later on map the various parts of the archive into these regions. In order to fix this we would have to completely rework the memory reserve/commit/uncommit logic on AIX which is currently out of our scope because of resource limitations. Unfortunately, I could not simply disable CDS in the configure step because some of the shared code apparently relies on parts of the CDS code which gets excluded from the build when CDS is disabled. So I also fixed the offending parts in hotspot and cleaned up the configure logic for CDS. Thank you and best regards, Volker PS: I did run the job through the submit forest (mach5-one-simonis-JDK-8204965-20180613-1946-26349) but the results weren't really useful because they mention build failures on linux-x64 which I can't reproduce locally.

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