how to know jvm is stopping the world?

[Li Li]

thanks.
is there any resources about writing tools communicating with JVM using
JVMTI?

On Tue, Dec 13, 2011 at 11:51 AM, Krystal Mok <rednaxelafx at gmail.com> wrote:

> The GC start/end events in JVMTI are available since a long time ago. You
> can use it in JDK 6 right now. [1] And in OpenJDK 7, too.
>
> The problem (for you) is this interface does not allow you to execute any
> Java code in the event callback. You'll need make some non-Java interface
> in your dispatcher so that this notification can ultimately propagate from
> the JVM in full GC to your dispatcher.
>
> - Kris
>
> [1]:
> http://docs.oracle.com/javase/6/docs/platform/jvmti/jvmti.html#GarbageCollectionStart
>
> On Tue, Dec 13, 2011 at 11:40 AM, Li Li <fancyerii at gmail.com> wrote:
>
>> That's what I want.
>> btw, this feature is only available in sun jdk7?
>> does it exist in openjdk7?
>>
>>
>> On Mon, Dec 12, 2011 at 11:06 PM, Stefan Karlsson <
>> stefan.karlsson at oracle.com> wrote:
>>
>>> On 12/11/2011 07:31 AM, Li Li wrote:
>>>
>>>> hi,
>>>>    In our application of full text searching with lucene and solr. we
>>>> will give jvm about 25GB memory. we use CMS as old generation garbage
>>>> collector. But the jvm sometimes can't do anything. So our clients complain
>>>> that the connection is time out. we find the reason is the jvm is doing
>>>> full gc and it will stop service for about 1-3 seconds.
>>>>    I know that this situation is inevitable when using CMS collector.
>>>> but we have more than one searching machines, so if I know jvm is doing
>>>> full gc(specially stop the world), I can send requests to other machines.
>>>> But the question now is that jvm don't provide an api for that. I think
>>>> it's not very difficult(for guys developing hotspot, but is in deed
>>>> difficult for me ). So I want your help.
>>>>    The first question is where is the position of CMS full gc.
>>>>    from http://blogs.oracle.com/**jonthecollector/entry/did_you_**know<http://blogs.oracle.com/jonthecollector/entry/did_you_know>
>>>>    there are many steps:
>>>>      1. STW initial mark
>>>>      2. Concurrent marking
>>>>      3. Concurrent precleaning
>>>>      4. STW remark
>>>>      5. Concurrent sweeping
>>>>      6. Concurrent reset
>>>>    there are 2 stop the world stages. I want to know the line number(or
>>>> functions) of this stages. so I can tell java program that jvm now is doing
>>>> full gc.
>>>>     The second is that how to communicate between jvm and java program?
>>>> My expected thing is like :
>>>>     //java program
>>>>     if(System.isStopTheWolrd()){
>>>>           //system is busy, tell the dispatch node that don't send
>>>> request to me
>>>>     }else{
>>>>           do service;
>>>>     }
>>>>     I have no experience in jvm developing. jvm is implemented in c and
>>>> jni is the interface between them. is there any other method that jvm can
>>>> achieve this? obviously, it can extend System class and add a static method
>>>> named isStopTheWorld(). Could some one tell me how to do this in details?
>>>> Thank you very much.
>>>>
>>>
>>> You could probably use JVMTI. See: http://docs.oracle.com/javase/**
>>> 7/docs/platform/jvmti/jvmti.**html#GarbageCollectionStart<http://docs.oracle.com/javase/7/docs/platform/jvmti/jvmti.html#GarbageCollectionStart>
>>>
>>> StefanK
>>>
>>
>>
>
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