RFR: 8169931: 8k class metaspace chunks misallocated from 4k chunk freelist

[Stefan Karlsson]

Thanks, Mikael.

StefanK

On 2016-11-22 17:08, Mikael Gerdin wrote:
> Hi Stefan,
>
>
> On 2016-11-22 15:54, Stefan Karlsson wrote:
>> Hi all,
>>
>> Please, review this patch to fix a bug in ChunkManager::list_index():
>>  http://cr.openjdk.java.net/~stefank/8169931/webrev.01
>
> The change looks good to me.
>
> /Mikael
>
>>
>> There's a great description of the bug in the bug report:
>>  https://bugs.openjdk.java.net/browse/JDK-8169931
>>
>> There are two conceptual parts of the metaspace. The _class_ metaspace,
>> and the _non-class_ metaspace. They have different chunk sizes, and
>> while querying for the list index of a humongous chunk in the class
>> metaspace, the code accidentally matched the size against the
>> MediumChunk size of the non-class metaspace.
>>
>> I've changed the code to not query against the global ChunkSizes enum,
>> but rather the values stored inside the ChunkManager instances.
>> Therefore, the list_index() function was changed into an instance 
>> method.
>>
>> I've written a unit test that provoked the bug. It's a simplified test
>> with vm asserts instead of gtest asserts. The reason is that the
>> ChunkManager class is currently located in metaspace.cpp, and is not
>> accessible from the gtest unit tests.
>>
>> Testing: jprt, Kitchensink, parallel class loading tests
>>
>> Thanks,
>> StefanK