[8u40] RFR: 8056240: Investigate increased GC remark time after class unloading changes in CRM Fuse

[Mikael Gerdin]

Hi Stefan,

On 2014-11-05 09:48, Stefan Karlsson wrote:
>
> On 2014-11-05 09:03, Stefan Karlsson wrote:
>> Hi all,
>>
>> Please, review the backport of this fix to 8u40:
>> http://cr.openjdk.java.net/~stefank/backports/8u40/8056240/webrev.01/
>>
>> I've attached the .rej files from applying the JDK 9 patch to JDK 8u40.
>
> The attachments were removed. The files can be found at:
> http://cr.openjdk.java.net/~stefank/backports/8u40/8056240/webrev.01/rej/

Thanks for posting the reject files, it made reviewing the backport much 
easier!

Looks good.

/Mikael

>
> thanks,
> StefanK
>
>>
>> Reasons for the .rej files from the failed applied patch hunks:
>>  metadataOnStackMark.cpp - the has_redefined_a_class parameter in
>> MetadataOnStackMark(bool has_redefined_a_class) is only present in JDK 9.
>>  metadataOnStackMark.hpp - the same as above
>>  classLoaderData.cpp - has_redefined_a_class parameter and JDK-8040237
>> isn't backported
>>  concurrentMark.cpp - JDK-8027450 isn't backported
>>
>> thanks,
>> StefanK
>>
>> On 2014-10-02 12:53, Stefan Karlsson wrote:
>>> Hi all,
>>>
>>> (The following patch changes HotSpot code in areas concerning GC, RT,
>>> and Compiler. So, it would be good to get reviews from all three teams.)
>>>
>>> Please, review this patch to optimize and parallelize the CodeCache
>>> part of MetadaOnStackMark.
>>>
>>> G1 performance measurements showed longer than expected remark times
>>> on an application using a lot of nmethods and Metadata. The cause for
>>> this performance regression was the call to
>>> CodeCache::alive_nmethods_do(nmethod::mark_on_stack); in
>>> MetadataOnStackMark. This code path is only taken when class
>>> redefinition is used. Class redefinition is typically used in
>>> monitoring and diagnostic frameworks.
>>>
>>> With this patch we now:
>>> 1) Filter out duplicate Metadata* entries instead of storing a
>>> Metadata* per visited metadata reference.
>>> 2) Collect the set of Metadata* entries in parallel. The code
>>> piggy-backs on the parallel CodeCache cleaning task.
>>>
>>> http://cr.openjdk.java.net/~stefank/8056240/webrev.00/
>>> https://bugs.openjdk.java.net/browse/JDK-8056240
>>>
>>> Functional testing:
>>> JPRT, Kitchensink, parallel_class_unloading, unit tests
>>>
>>> Performance testing:
>>> CRM Fuse - where the regression was found
>>>
>>> The patch changes HotSpot code in areas concerning GC, RT, Compiler,
>>> and Serviceability. It would be good to get some reviews from the
>>> other teams, and not only from the GC team.
>>>
>>> thanks,
>>> StefanK
>>
>