[concurrency-interest] Suspecting a problem in recent jdk-9 builds
ati at activeviam.com
Fri Dec 30 12:03:50 EST 2016
Thank you for all your answers.
We tried to run jcstress and all the tests passed without any error.
Our application uses several TBs of RAM, so we need to use G1GC. The
problem still occurs when adding -XX:-UseBiasedLocking to the VM args. We
are going to try building the application with the commit corresponding to
the addition of the VarHandles and the one just before to see if we can
narrow the problem down to this change.
Note that we are a partner of Oracle and we are running our application on
the Oracle network, so it is accessible by the JVM engineers. Let us know
if you need to arrange access to the application.
On Wed, Dec 28, 2016 at 5:56 PM, Martin Buchholz <martinrb at google.com>
> Experience suggests that such problems are *usually* in the application
> code, but of course there are undiscovered bugs in java.util.concurrent.
> Since only you can reproduce the problem, only you can narrow down the
> possible root causes. You could build your own openjdk9, bisect to the
> exact commit that is causing problems, but it would be a lot of work, and
> it might in the end be a change to hotspot gc, with root cause still
> On Wed, Dec 28, 2016 at 1:30 AM, Antoine Tissier <ati at activeviam.com>
>> We have been running benchmarks for our in-memory analytics software
>> ActivePivot on a M6.32 machine (Solaris Sparc, 8 TB RAM, 2304 logical cores
>> (288 physical cores)).
>> Our benchmarks involve high parallelism along with many queries divided
>> in a high number of tasks (CountedCompleters) in the ForkJoinPool. With
>> build 145 of jdk-9, some tasks are not executed, causing larger completion
>> problems. However, with the earlier build 111, the problem does not occur.
>> On a smaller Linux machine (Linux amd 64, 64 logical cores (32 physical
>> cores), 512 GB RAM) but with a similar setup, the problem was not
>> The problem seems to arise when a large number of completers (>20 000)
>> are involved: forking tasks works well but when submitting tasks to a new
>> pool, it seems that their compute method is sometimes not called.
>> We indeed log every call to ForkJoinPool.submit, as well as everytime a
>> completer enters its compute method, and clearly see that once in a while,
>> the task is never computed after having been submitted. We let the system
>> run for an additional hour, and there was no more progress even though the
>> system was idle. Thread dumps did not show any suspect activity (all worker
>> threads were idle).
>> We tried to reproduce the problem with a similar but more simple test,
>> but it was not successful.
>> Are you aware of any concurrency/task completion problems in the more
>> recent builds of jdk-9 ?
>> Are there any additional tests that we could run in order to diagnose
>> this issue ?
>> Best regards,
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>> <https://www.youtube.com/channel/UCGjYnbjlPamN0RvSm3eGqCw> Antoine
>> *Junior Software Engineer*
>> [image: Mobile]+33(0) 126.96.36.199.62 <+33%206%2026%2033%2035%2062>
>> [image: Skype]antoine_tissier
>> [image: Website]www.activeviam.com <https://activeviam.com/>
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46 rue de l'Arbre Sec, 75001 Paris
[image: Twitter] <https://twitter.com/active_viam> [image: Blog]
<http://activeviam.com/blog/> [image: Linkedin]
<https://www.linkedin.com/company/85029> [image: Youtube]
<https://www.youtube.com/channel/UCGjYnbjlPamN0RvSm3eGqCw> Antoine Tissier
*Junior Software Engineer*
[image: Mobile]+33(0) 188.8.131.52.62
[image: Website]www.activeviam.com <https://activeviam.com/>
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