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

Jesper Wilhelmsson jesper.wilhelmsson at oracle.com
Wed Feb 11 17:08:38 UTC 2015

Mikael Gerdin skrev den 11/2/15 15:08:
> On 2015-02-11 11:30, Jesper Wilhelmsson wrote:
>> Kim Barrett skrev den 11/2/15 00:03:
>>> 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?
>> We can't reopen the old issue since it has already been used to push a
>> change. The procedure is to create a REDO issue by cloning the original
>> issue. I have done that now.
> Right, I was planning to do that but I forgot about it. Thanks Kim for pointing
> that out and Jesper for fixing it.

No problem, that's part of the gatekeeping duties :)
Another thing we should remember the next time this happens is that if the 
change has already been promoted to jdk9/hs, the backout should be done directly 
in jdk9/hs to enable other teams to benefit from the backout asap.
I should have mentioned that when we talked about this before you did the 
backout. My fault.

> /Mikael
>> /Jesper

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