G1 Old Generation GC collection event not sent after Mixed evacuation pause

[Jenny Zhang]

You are right about the mixed gc reclaiming old gen. If I understand you 
correctly, your question is about why initial marking is young gc? It 
only collects young gen.

thanks

Jenny


On 7/19/2017 12:15 PM, Sundara Mohan M wrote:
> From the document, i see Space reclamation phase (multiple mixed 
> collections) is when the object from old gen is collected. So 
> shouldn't we get notified via OldGen GarbageCollectorMXBean instead of 
> YoungGen MXBean?
>
> I am still trying to understand if this was designed to be like this 
> because of logical space/generation in G1GC or it is a bug?
>
> Thanks
> Sundar
>
> On Wed, Jul 19, 2017 at 12:09 PM, Jenny Zhang <yu.zhang at oracle.com 
> <mailto:yu.zhang at oracle.com>> wrote:
>
>     Sundar,
>
>     Initial mark is a young gc piggy backed with some initial marking
>     activities.
>
>     "Initial Mark : This type of collection starts the marking process
>     in addition to performing a regular young-only collection.
>     Concurrent marking determines all currently reachable (live)
>     objects in the old generation regions to be kept for the following
>     space-reclamation phase. While marking hasn’t completely finished,
>     regular young collections may occur. Marking finishes with two
>     special stop-the-world pauses: Remark and Cleanup."
>
>     From
>     http://docs.oracle.com/javase/9/gctuning/garbage-first-garbage-collector.htm#JSGCT-GUID-1CDEB6B6-9463-4998-815D-05E095BFBD0F
>     <http://docs.oracle.com/javase/9/gctuning/garbage-first-garbage-collector.htm#JSGCT-GUID-1CDEB6B6-9463-4998-815D-05E095BFBD0F>
>
>     Thanks
>
>     Jenny
>
>
>     On 7/19/2017 11:03 AM, Sundara Mohan M wrote:
>>     Jenny,
>>        Thanks for the update.
>>
>>     Another question i was looking at the source and saw this,
>>
>>     enum G1YCType {
>>       Normal,
>>       InitialMark,
>>       DuringMark,
>>       Mixed,
>>       G1YCTypeEndSentinel
>>     };
>>
>>
>>     Any idea why InitialMark are categorized as Young Collection,
>>     though it is processing in Old Generation?
>>     Also mixed can include old regions in which case it should be
>>     categorized as Old Generation.
>>
>>     Just trying to understand if this is designed like this or this
>>     is kind of bug?
>>
>>
>>     Thanks,
>>     Sundar
>>
>>     On Wed, Jul 19, 2017 at 8:24 AM, yu.zhang at oracle.com
>>     <mailto:yu.zhang at oracle.com> <yu.zhang at oracle.com
>>     <mailto:yu.zhang at oracle.com>> wrote:
>>
>>         Sundara,
>>
>>         I have filed this bug
>>         https://bugs.openjdk.java.net/browse/JDK-8145923
>>         <https://bugs.openjdk.java.net/browse/JDK-8145923>
>>
>>         But has not been fixed.
>>
>>         Jenny
>>
>>
>>         On 07/18/2017 10:41 AM, Sundara Mohan M wrote:
>>>         Hi,
>>>            I am trying to capture all GC event happened on G1 Old
>>>         Generation.
>>>         I was expecting when G1 Evacuation pause (mixed) happens it
>>>         should trigger event to my app but instead, i am getting
>>>         notification only when Full GC happens.
>>>
>>>         Here is what i am doing
>>>         gcMxBeanListener = myFunction(...)
>>>         oldGen  = ManagementFactiory.getGarbageCollectorMXBeans find
>>>         { "G1 Old Generation" }
>>>         oldGen.addNotificationListener(gcMxBeanListener, null, null)
>>>
>>>         But in the case of CMS GC, it is triggered when the
>>>         concurrent cycle is completed.
>>>
>>>
>>>         Is there something i am missing?
>>>
>>>         Thanks,
>>>         Sundar
>>>
>>>
>>>         _______________________________________________
>>>         hotspot-gc-use mailing list
>>>         hotspot-gc-use at openjdk.java.net
>>>         <mailto:hotspot-gc-use at openjdk.java.net>
>>>         http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
>>>         <http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use>
>>
>>
>
>

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