RFR: 8170395: Metaspace initialization queries the wrong chunk freelist
stefan.karlsson at oracle.com
Mon Nov 28 19:29:29 UTC 2016
On 2016-11-28 14:57, Michail Chernov wrote:
> Hi Stefan,
> Could you please add simple regression test for this case?
The failure below was found with one of the test cases in:
Is this enough or do you want an explicit regression test that simply
java -XX:InitialBootClassLoaderMetaspaceSize=30720 -version ?
> On 28.11.2016 16:52, Stefan Karlsson wrote:
>> Hi all,
>> Please, review this patch to fix metaspace initialization.
>> The fix for JDK-8169931 introduced a new assert to ensure that we
>> always try to allocate chunks that are any of the three fixed sizes
>> (specialized, small, medium) or a humongous chunk (if it is larger
>> then the medium chunk size).
>> During metaspace initialization an initial metaspace chunk is
>> allocated. The size of some of the metaspace instances can be
>> specified on the command line. For example:
>> java -XX:InitialBootClassLoaderMetaspaceSize=30720 -version
>> If this size is smaller than the medium chunk size and at the same
>> time doesn't match the specialized or small chunk size, then we end
>> up hitting the assert mentioned above:
>> # Internal Error
>> pid=31643, tid=31646
>> # assert(size > free_chunks(MediumIndex)->size()) failed: Not a
>> humongous chunk
>> The most important part of the fix is this line:
>> + // Adjust to one of the fixed chunk sizes (unless humongous)
>> + const size_t adjusted = adjust_initial_chunk_size(requested);
>> which ensures that we always request either of a specialized, small,
>> medium, or humongous chunk size, even if the requested size is
>> neither of these.
>> Most of the other code is refactoring to unify the non-class
>> metaspace and the class metaspace code paths to get rid of some of
>> the existing code duplication, bring the chunk size calculation
>> nearer to the the actual chunk allocation, and make it easier to
>> write a unit test for the new adjust_initial_chunk_size function.
>> The patch for JDK-8169931 was backed out with JDK-8170355 and will be
>> reintroduced as JDK-8170358 when this patch has been reviewed and
>> Testing: jprt, unit test, parts of PIT testing (including CDS tests),
>> failing test
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