RFR: (S): JDK-8213323: sa/TestJmapCoreMetaspace.java and sa/TestJmapCore.java fail with ZGC

[Jini George]

Thank you very much, JC, for looking into this.

http://mail.openjdk.java.net/pipermail/zgc-dev/2018-August/000455.html

The link above provides an explanation of why it is difficult to support 
ZGC with SA where there is an iteration over the heap. And currently, I 
am unsure as to whether we will devise a way to overcome this issue. We 
currently have the following JBS entry for tracking this.

https://bugs.openjdk.java.net/browse/JDK-8207843 (SA: Add support for 
Object Histogram with ZGC)

I have added a comment in the ER above to keep track of enabling the 
tests if this is resolved.

I agree with your comment on throwing a RuntimeException. Doing this 
avoids the misleading "heap written to" message. I will modify this and 
remove the ';' you pointed out and post another webrev.

Thank you,
Jini.



On 11/9/2018 9:36 PM, JC Beyler wrote:
> Hi Jini,
> 
> The webrev looks good to me as well except for a few questions/comments:
> 
> I have a generic question that is related to the webrev:
>    - Are there plans at some point for Jmap to support ZGC heaps in the 
> future ? Or is this infeasible?
>          I ask because if a lot of tests are disabled for ZGC for a 
> limited amount of time (in order to provide time for future support) 
> there should be a means to scrub the tests at a later date to see which 
> are now supported, no?
> 
>    - In 
> http://cr.openjdk.java.net/~jgeorge/8213323/webrev.00/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java.html:
> 
>   397         if (vm.getUniverse().heap() instanceof ZCollectedHeap) {
>   398             System.err.println("WARNING: Operation not supported 
> for ZGC.");
>   399             return;
>   400         };
> 
>       - 1 nit is the ';'  after the closing '}'
>       - Should the code throw a RuntimeException instead? Just printing 
> an error seems "weak" for me when this really won't work. Of course, 
> that means tracking the callers now of write and probably adding 
> exception handling there and I'm not sure that is something that is 
> warranted here but thought I would ask :)
> 
> Thanks!
> Jc
> 
> 
> 
> Thanks,
> Jc
> 
> On Fri, Nov 9, 2018 at 1:47 AM gary.adams at oracle.com 
> <mailto:gary.adams at oracle.com> <gary.adams at oracle.com 
> <mailto:gary.adams at oracle.com>> wrote:
> 
>     Looks OK to me.
> 
>     On 11/9/18 1:40 AM, Jini George wrote:
>      > Hello!
>      >
>      > Requesting reviews for a small change for disabling the testing of
>      > TestJmapCoreMetaspace.java and TestJmapCore.java with ZGC. The
>     change
>      > also includes skipping of creating the heapdump file with jmap if
>     the
>      > GC being used is ZGC.
>      >
>      > Webrev: http://cr.openjdk.java.net/~jgeorge/8213323/webrev.00/
>      > Bug ID: https://bugs.openjdk.java.net/browse/JDK-8213323
>      >
>      > Thanks,
>      > Jini.
> 
> 
> 
> 
> -- 
> 
> Thanks,
> Jc