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

[Stefan Karlsson]

Hi Coleen,

On 2016-11-22 20:30, Coleen Phillimore wrote:
>
> Can you put this test at the end of the file with // Unit Tests and an 
> explanation why this is here so people don't try to port the whole 
> thing to gtest?

Sure.

>
> I was looking for uses of list_index and found this code, which looks 
> wrong:
>
>   assert((word_size <= chunk->word_size()) ||
>          list_index(chunk->word_size() == HumongousIndex),
>          "Non-humongous variable sized chunk");

I'll fix that assert.

>
>
> This change looks good though.

Thanks, I'll send out a new patch.

StefanK

>
> Thanks,
> Coleen
>
> On 11/22/16 9:54 AM, 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
>>
>> 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
>