RFR: 8012241 NMT huge memory footprint, it usually leads to OOME

Zhengyu Gu zhengyu.gu at oracle.com
Thu Jul 11 09:49:38 PDT 2013


Hi Dan,

Thanks for the review.


On 7/11/2013 12:11 PM, Daniel D. Daugherty wrote:
> > http://cr.openjdk.java.net/%7Ezgu/8012241/webrev.00
>
> src/share/vm/services/memTracker.cpp
>     I noticed that the NMT shutdown code path calls:
>
>     200   // shutdown shared decoder instance, since it is only
>     201   // used by native memory tracking so far.
>     202   Decoder::shutdown();
>
>     Isn't the Decoder used by the trouble shooting code at this point?
>     If so, will this NMT shutdown cause hs_err_pid generation to not
>     be able to generate crash info with symbols?
>
VMError uses a private instance of decoder, since error handling path 
can not take any lock.
NMT uses shared instance. Right  now, only NMT uses this instance, and 
the instance can be re-created.

Thanks,

-Zhengyu


> Dan
>
>
> On 7/11/13 7:07 AM, Zhengyu Gu wrote:
>> The patch is a workaround that prevents JVM from OOM when running 
>> Kitchensink with NMT on some slow machines.
>>
>> Kitchensink normally runs with about 100 threads, peaks around 150 
>> threads. On some slow machines, NMT worker thread does not process 
>> raw NMT data quick enough, that causes huge backlogs, which consumes 
>> large amount of memory and can lead JVM OOM. By enforcing the new 
>> threshold, NMT will shutdown itself and free NMT memory.
>>
>> If native memory tracking is important to diagnostic memory issue, 
>> user can use -XX:-AutoShutdownNMT diagnostic flag to override above 
>> behavior. Turning off auto shutdown NMT flag, NMT also tries slow 
>> down malloc/free rate, to give NMT worker thread a chance to catch up.
>>
>>
>> JBS: https://jbs.oracle.com/bugs/browse/JDK-8012241
>> Exteneral bug: not available
>> Webrev: http://cr.openjdk.java.net/~zgu/8012241/webrev.00/ 
>> <http://cr.openjdk.java.net/%7Ezgu/8012241/webrev.00/>
>>
>>
>> Tests:
>>   Christian Tornqvist has verified on Windows and Solaris, that patch 
>> prevented JVM from OOM.
>>
>> Thanks,
>>
>> -Zhengyu
>



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