Unreachable Memory not freed

[Jenny Zhang]

Hi, Thorsten,

I can reproduce this with a micro. I have filed 
https://bugs.openjdk.java.net/browse/JDK-8173594

The micro is mostly based on 
http://stackoverflow.com/questions/26027313/how-to-load-and-parse-svg-documents 
with some modification. I will upload the micro and details later.

I think this is a issue how jvmti and gc reporting unreachable objects. 
Those objects should not be reported as unreachable.

Thanks
Jenny

On 1/25/2017 3:23 PM, yu.zhang at oracle.com wrote:
> Thorsten,
>
> Thanks very much for the heap dump and gc log.
>
> I assume the gc log and heap dump are from the same run. It is very 
> interesting, in the gc log:
>
> 2017-01-24T16:41:17.184-0100: 1301.633: [Full GC (Heap Dump Initiated 
> GC)  3817M->3816M(4096M), 8.9543444 secs]
>    [Eden: 2048.0K(2048.0M)->0.0B(2048.0M) Survivors: 0.0B->0.0B Heap: 
> 3817.7M(4096.0M)->3816.2M(4096.0M)], [Metaspace: 
> 142921K->142921K(1175552K)]
>  [Times: user=16.35 sys=0.11, real=8.95 secs]
>
> GC thinks there are 3816.2M of objects alive. But in the heap dump, 
> there is only 1.8G alive.
>
> I can see those unreachable objects with yourkit, mostly are
>
> org.apache.batik.dom.GenerecText
>
> But apparently gc does not think those are dead. It could be a bug in 
> gc, or jvmti dumping the heap, or tool(yourkit, apache MAT). I need to 
> discuss this with dev team.
>
> Back to the gc log, it seems the application allocates a lot of 
> humongous objects. I can see some int[] of 1.5m. In general the heap 
> is very full, with a lot of to-space exhausted, and full gc. And the 
> heap usage after full gc is almost the whole heap (4096M).
>
> Thanks
>
> Jenny
>
>
> On 01/25/2017 01:15 AM, Thorsten Goetzke wrote:
>> Hello,
>>
>> You can find the heap dump and gc logs under 
>> https://filesender.freigmbh.de/filesender/?vid=10f1aeb6-82b4-3d09-c201-00002042c681
>>
>> Link is valid until 28.01.2017 (1/28/2017). Feel free to message me 
>> if you need a reupload.
>>
>> Best Regards,
>> Thorsten
>>
>>
>>> Thorsten,
>>>
>>> Can you please put the heap dump and gc logs somewhere for download?
>>>
>>> Thanks
>>> Jenny
>>>
>>> On 1/24/2017 8:30 AM, Thorsten Goetzke wrote:
>>>> Hello,
>>>>
>>>> I am working on a closed source software that uses a patched version
>>>> of apache-batik to display SVG-Documents one by one. If you keep
>>>> loading and discarding some specific SVG-Documents memory consumption
>>>> keeps on growing until it reaches more than 95% of the available
>>>> memory. The application becomes unusable slow, very little memory gets
>>>> freed, although the gc is constantly running. Sometimes an
>>>> OutOfMemoryError gets thrown. I took memory snaphsots and analyzed
>>>> them using jvisualvm and yourkit. These tools report the majority of
>>>> the memory as unreachable.
>>>> I have tried different garbage collectors (G1,ConcurrentMarkSweep),
>>>> and different Versions of Java: 1.8_60;1.8_65;1.8_102, the issue is
>>>> always reproducible.
>>>> Is there something i can do to debug this further? I am currently not
>>>> able to reproduce this issue in a somewhat small self contained 
>>>> example.
>>>> I could provide gc-logs and the heap dump (about 1gb zipped) or any
>>>> other debuging info if someone is interested.
>>>>
>>>> Best Regards,
>>>> Thorsten Goetzke
>>>>
>>
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>