RFR: 8057037: Verification in ClassLoaderData::is_alive is too slow

Volker Simonis volker.simonis at gmail.com
Wed Apr 8 13:04:11 UTC 2015


Great!

Thanks a lot,
Volker


On Wed, Apr 8, 2015 at 2:56 PM, Stefan Karlsson
<stefan.karlsson at oracle.com> wrote:
> Hi Volker,
>
> On 2015-04-08 14:45, Volker Simonis wrote:
>>
>> Hi Stefan,
>>
>> have you considered downporting this to 8u-dev?
>
>
> This should have been backported earlier, sorry.
>
>> I would do it myself, but unfortunately it is in shared code so I
>> would need a sponsor anyway.
>>
>> This hurts us badly especially on our slow porting platforms where we
>> get GC-times of several minutes now.
>
>
> The patch applies cleanly to:
> http://hg.openjdk.java.net/jdk8u/hs-dev/hotspot/
>
> so I'm going to push the fix to that repository.
>
> Thanks,
> StefanK
>
>>
>> Thank you and best regards,
>> Volker
>>
>> On Tue, Sep 2, 2014 at 3:03 PM, Stefan Karlsson
>> <stefan.karlsson at oracle.com> wrote:
>>>
>>> Hi all,
>>>
>>> Please review this patch to remove some verification code that was added
>>> during the G1 Class Unloading project. The code was added to make sure we
>>> catch any class unloading bugs as early as possible. This verification
>>> code
>>> is run too often and is causing large GC times in our fastdebug test
>>> runs.
>>> In one of the tests I investigated, the Full GCs take 8 seconds with this
>>> verification and 0.2 seconds without it. Most of the verified pointers
>>> are
>>> already verified before and after GCs in ClassLoaderDataGraph::verify().
>>>
>>> http://cr.openjdk.java.net/~stefank/8057037/webrev.00/
>>>
>>> thanks,
>>> StefanK
>
>


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