Debugging high JNI Weak Reference times

[Tao Mao]

Hi Bharat,

Then, the weird thing is: -XX:+ParallelRefProcEnabled did help reduce JNI
weak references processing to ~10 sec in your case while the ticket says
that JNI weak ref processing is single-threaded even with
ParallelRefProcEnabled
on.

Thanks.

On Wed, Feb 25, 2015 at 3:19 PM, bharat naik <bharat.2511 at gmail.com> wrote:

> Hi Tao,
>
> Thanks for the reply,but this occurrence was because JNI weak reference
> processing isn't done in parallel currently.
> A bug has been filed regarding this: JDK-8072498
> <https://bugs.openjdk.java.net/browse/JDK-8072498>
>
> Thanks,
> Bharat.
>
> On Wed, Feb 25, 2015 at 3:01 PM, Tao Mao <yiyeguhu at gmail.com> wrote:
>
>> Hi Bharat,
>>
>> Please attach your gc log with at least the following options
>> "-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps"
>>
>> Regards,
>> Tao Mao
>>
>>
>> On Tue, Feb 3, 2015 at 4:31 PM, bharat naik <bharat.2511 at gmail.com>
>> wrote:
>>
>>> Hi all,
>>>
>>> We used to see a high amount of time spent during the rescan phase of
>>> GC, i..e the weak refs processing part used to take around 140 seconds.
>>> This would occur about 3-4 times for every 70 runs.
>>>
>>> We set the following options:  -XX:+ParallelRefProcEnabled  and
>>>  -XX:+PrintReferenceGC to get more details and as a workaround. The
>>> time reduced to ~10 seconds and we see that most of it is spent in
>>> resolving JNI weak references.
>>>
>>> I did see a few similar problems on the net but they were all related to
>>> the G1 GC and we use CMS. How does one usually go about debugging further
>>> in this scenario and are there any other options that we could try to help
>>> mitigate this problem?
>>>
>>> Java version is:
>>> java version "1.7.0_45"
>>>
>>> Java(TM) SE Runtime Environment (build 1.7.0_45-b18)
>>>
>>> Java HotSpot(TM) 64-Bit Server VM (build 24.45-b08, mixed mode)
>>>
>>> These are the relevant GC options:
>>>
>>> -XX:+UseCompressedOops
>>>
>>> -XX:SurvivorRatio=3
>>>
>>> -XX:+UseLargePages
>>>
>>> -XX:TargetSurvivorRatio=90
>>>
>>>  -XX:+AlwaysPreTouch
>>>
>>> -XX:+AggressiveOpts
>>>
>>> -XX:+UseNUMA
>>>
>>> -XX:+UseTLAB
>>>
>>> -XX:+UseParNewGC
>>>
>>> -XX:+UseConcMarkSweepGC -
>>>
>>> -XX:CMSWaitDuration=90000
>>>
>>> -XX:+ParallelRefProcEnabled
>>>
>>> -XX:+PrintReferenceGC
>>>
>>> -XX:+PrintJNIGCStalls
>>>
>>> -XX:ParallelCMSThreads=16
>>>
>>> -XX:+CMSScavengeBeforeRemark
>>>
>>> -XX:-CMSConcurrentMTEnabled
>>>
>>> -XX:CMSInitiatingOccupancyFraction=10
>>>
>>> -XX:+UseCMSInitiatingOccupancyOnly
>>>
>>>
>>> Any help is appreciated!
>>>
>>>
>>> Thanks,
>>>
>>> Bharat.
>>>
>>>
>>>
>>> _______________________________________________
>>> hotspot-gc-use mailing list
>>> hotspot-gc-use at openjdk.java.net
>>> http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
>>>
>>>
>>
>
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