RFR (S) 8072693: [BACKOUT] GCCause should distinguish jcmd GC.run from System.gc()

[Kim Barrett]

On Feb 6, 2015, at 10:10 AM, Mikael Gerdin <mikael.gerdin at oracle.com> wrote:
> 
> Hi all,
> 
> There are some problems with the Diagnostic Command GCCause change, I suggest that we back out the change and reconsider its implementation.
> 
> [from the bug]
> The change is incomplete since several places in the GC code assumes that explicit gcs have the _java_lang_system_gc GCCause value in order to determine the behavior.
> For example:
> ParallelGC does not apply policy decisions on user-invoked GCs (decided by the GCCause)
> G1/CMS honors +ExplicitGCInvokesConcurrent based on the GCCause setting.
> This could cause problems for people expecting concurrent gcs when running the diagnostic command instead of a possibly several-second full gc pause.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8072693
> Webrev: http://cr.openjdk.java.net/~mgerdin/8072693/webrev.0/

A procedural question: Shouldn't this backout be accompanied by re-opening the original RFE (JDK-8068589) that was resolved by the changeset that is now being backed out?