RFR (XS) 8205702: assert(UseCompressedClassPointers) failed in universe.hpp

[Per Liden]

Updated webrev, which adjusts the @requires tag, from:

   @requires vm.cds & vm.gc != "Z"

to:

   @requires vm.cds.archived.java.heap

which I believe is more correct in this case.

http://cr.openjdk.java.net/~pliden/8205702/webrev.1

cheers,
Per


On 06/27/2018 09:15 AM, Per Liden wrote:
> Hi Coleen,
> 
> This doesn't look quite right to me. ZGC already disables 
> UseCompressedOop and UseCompressedClassPointers, which should be the 
> indicators that we can't use CDS. The problem is that CDS checks those 
> flags _before_ the heap has had a change to say they it supports. So if 
> we just move the call to set_shared_spaces_flags() after the call to 
> GCConfig::arguments()->initialize() (which should be safe), then we're 
> all good and you'll get the usual:
> 
> $ ./build/fastdebug/images/jdk/bin/java -Xshare:dump 
> -XX:+UnlockExperimentalVMOptions -XX:+UseZGC
> Error occurred during initialization of VM
> Cannot dump shared archive when UseCompressedOops or 
> UseCompressedClassPointers is off.
> 
> Here's a proposed patch for this, which also adjusts the appropriate 
> tests for this:
> 
> http://cr.openjdk.java.net/~pliden/8205702/webrev.0
> 
> cheers,
> Per
> 
> On 06/27/2018 01:09 AM, coleen.phillimore at oracle.com wrote:
>>
>> Hi Calvin, thank you for reporting the bug and the code review and 
>> test code.
>>
>> On 6/26/18 5:42 PM, Calvin Cheung wrote:
>>> Hi Coleen,
>>>
>>> The code changes look good.
>>>
>>> Since there's a new error message, I'd suggest adding a test to 
>>> runtime/SharedArchiveFile/SharedArchiveFile.java as follows:
>>>
>>> diff --git 
>>> a/test/hotspot/jtreg/runtime/SharedArchiveFile/SharedArchiveFile.java 
>>> b/test/hotspot/jtreg/runtime/SharedArchiveFile/SharedArchiveFile.java
>>> --- 
>>> a/test/hotspot/jtreg/runtime/SharedArchiveFile/SharedArchiveFile.java
>>> +++ 
>>> b/test/hotspot/jtreg/runtime/SharedArchiveFile/SharedArchiveFile.java
>>> @@ -52,5 +52,13 @@
>>>                                "-Xshare:on", "-version");
>>>          out = CDSTestUtils.executeAndLog(pb, "SharedArchiveFile");
>>>          CDSTestUtils.checkExec(out);
>>> +
>>> +        // CDS dumping doesn't work with ZGC
>>> +        ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(true,
>>> + "-XX:SharedArchiveFile=./SharedArchiveFile.jsa",
>>> +                                "-XX:+UseZGC",
>>> +                                "-Xshare:dump");
>>> +        out = CDSTestUtils.executeAndLog(pb, "SharedArchiveFile");
>>> +        CDSTestUtils.checkExecExpectError(out, 1, "DumpSharedSpaces 
>>> (-Xshare:dump) is not supported with ZGC.");
>>>      }
>>>  }
>>>
>>> (I haven't tested the above)
>>
>> It needed an -XX:+UnlockExperimentalVMOptions as well, and not reclare 
>> pb.
>>
>> open webrev at http://cr.openjdk.java.net/~coleenp/8205702.02/webrev
>>
>>>
>>> Also, I think the new error message should be included in the release 
>>> notes.
>>>
>>
>> I added the test case and it passes.  I don't think having a release 
>> note for something that nobody would ever do for an experimental 
>> option is worth having.   But I can look into the ZGC release notes 
>> and see if there's something that says CDS is not supported.
>>
>> Thanks,
>> Coleen
>>> thanks,
>>> Calvin
>>>
>>> On 6/26/18, 2:13 PM, coleen.phillimore at oracle.com wrote:
>>>> Summary: Disable CDS with ZGC
>>>>
>>>> Tested with:
>>>> java -XX:+UnlockExperimentalVMOptions -XX:+UseZGC -Xshare:dump
>>>> java -XX:+UnlockExperimentalOptions -XX:+UseZGC -Xshare:on -version
>>>>
>>>> open webrev at http://cr.openjdk.java.net/~coleenp/8205702.01/webrev
>>>> bug link https://bugs.openjdk.java.net/browse/JDK-8205702
>>>>
>>>> Thanks,
>>>> Coleen
>>