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

David Holmes david.holmes at oracle.com
Mon Jun 18 06:17:04 UTC 2018

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!)

src/hotspot/share/classfile/javaClasses.cpp

AFAICS you should be using INCLUDE_CDS in the ifdefs not INCLUDE_CDS_JAVA_HEAP. 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 is_archive_object(oop p) NOT_CDS_JAVA_HEAP_RETURN_(false); ./hotspot/share/classfile/stringTable.hpp: static oop create_archived_string(oop s, Thread* THREAD) NOT_CDS_JAVA_HEAP_RETURN_(NULL);

so these methods should be defined when CDS is not available.

??

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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