Closed roded closed 3 weeks ago
Hi @roded ,
Would you please confirm which GC policy is used? Based on newspace=0/0
I can guess optthruput
or optavgpause
.
"Java Heap Space" reason is quite restrictive, the problem should be related to object heap usage directly.
There is not enough data for investigation obviously. So I am speculating here.
There is might be a case "ExcessiveGC" condition detected (potentially incorrectly). Excessive GC is as condition when GC operations take too much time (95%+ of total JVM times consumption) or produced too few free space (less than 5%). In this case OOM Java Heap Space is enforced even there is free space in the heap. GC is able to release a lot of space (from 627478544 to 5745756904 bytes) so it is not a latter one. We had problems in the past when ExcessiveGC can be detected incorrectly due inconsistent wall clock reading (like end of operation has a smaller time stamp than it's beginning - due clock adjustment during the operation). This issue has been fixed but might be we have something similar here.
If you have Snap trace file (.trc
) you can convert it to the text file java com.ibm.jvm.TraceFormat <input_file>
end search for "ExcessiveGC". It would be helpful if you can share Snap trace file.
Another potential reason might be low memory below 4GB bar (as far as this is Compressed Refs JVM). In this case you should see mentioning of this in a few lines on the top of javacore.
Really this should be handled via IBM support. @paulcheeseman @manqingl fyi
Thanks for the reply and explanations @dmitripivkine.
GC policy is: -Xgcpolicy:optthruput
.
I don't see any mention of low below the bar storage at the top of the javacore, not entirely sure what to look for though.
Let me check about the snap trace file.
Really this should be handled via IBM support.
Agreed. @roded please open a support case at https://www.ibm.com/mysupport/
I've opened a case with IBM support. For future reference, could someone please explain when an IBM support case is relevant vs an issue in this repository? Thanks!
IBM Java 8 is an IBM product that uses the OpenJ9 open source. This repo is used by OpenJ9 developers, not IBM support staff.
Another point is that issues in this open source repo get free best effort responses, there are no guarantees for replies.
Understood. Thank you.
Java -version output
Summary of problem
JVM is running with a Xmx of 6GB. User is reporting an OOM for which we have the javacore dump (but can't currently share).
Heap space is fine:
As are other segment types (i.e., they have free space available).
However the JIT Data Cache seems exhausted? But I'm not sure if
Total memory free
is always 0 for the JIT Data Cache.Any pointers would be much appreciated. Thank you.
Diagnostic files
OutOfMemoryError: Java Heap Space
N/A?