On 27/10/2016 6:36 PM, Staffan Larsen wrote:
All,
Please review this small patch to remove the requirement
-XX:+UnlockDiagnosticVMOptions when running the GC.class_stats diagnostic
command. Diagnostic commands are used for diagnosing problems and should not
require restarting the JVM with a different command line flag if this can be
avoided.
Right - it doesn't make sense to have to use UnlockDiagnosticVMOptions
to run any diagnostic Dcmd. Otherwise it should be a requirement for all.
While fixing this I also noticed that VM.print_touched_methods said it required
-XX:+UnlockDiagnosticVMOptions, while what it really required was
-XX:+LogTouchedMethods (which in turn requires -XX:+UnlockDiagnosticVMOptions)
so I changed the error message here. In this case I think it is ok to require a
special command line flag since collecting the information comes with an
overhead.
The only reason a Dcmd should require a specific VM option is if the
Dcmd will not be able to function unless the VM was started with that
option - IMHO :) Is that the case for LogTouchedMethods?
Thanks,
David
I have verified the fix manually and by running these tests:
hotspot/test/runtime/CommandLine/PrintTouchedMethods.java
hotspot/test/serviceability/sa/TestInstanceKlassSize.java
hotspot/test/serviceability/sa/TestInstanceKlassSizeForInterface.java
bug: https://bugs.openjdk.java.net/browse/JDK-8168305
webrev: http://cr.openjdk.java.net/~sla/8168305/webrev.01/
Thanks,
/Staffan
