RFR(L): 8195097: Make it possible to process StringTable outside safepoint

[Robbin Ehn]

Thanks Coleen!

/Robbin

On 2018-06-05 20:57, coleen.phillimore at oracle.com wrote:
> 
> This latest version looks good to me also.
> Coleen
> 
> On 6/4/18 11:59 AM, Robbin Ehn wrote:
>> Hi,
>>
>> Here is an updated after reviews:
>> Inc : http://cr.openjdk.java.net/~rehn/8195097/v2/inc/webrev/
>> Full: http://cr.openjdk.java.net/~rehn/8195097/v2/full/webrev/
>>
>> Passed tier 1-3.
>>
>> /Robbin
>>
>>
>> On 2018-05-28 15:19, Robbin Ehn wrote:
>>> Hi all, please review.
>>>
>>> This implements the StringTable with the ConcurrentHashtable for managing the
>>> strings using oopStorage for backing the actual oops via WeakHandles.
>>>
>>> The unlinking and freeing of hashtable nodes is moved outside the safepoint,
>>> which means GC only needs to walk the oopStorage, either concurrently or in a
>>> safepoint. Walking oopStorage is also faster so there is a good effect on all
>>> safepoints visiting the oops.
>>>
>>> The unlinking and freeing happens during inserts when dead weak oops are
>>> encountered in that bucket. In any normal workload the stringtable self-cleans
>>> without needing any additional cleaning. Cleaning/unlinking can also be done
>>> concurrently via the ServiceThread, it is started when we have a high ‘dead
>>> factor’. E.g. application have a lot of interned string removes the references
>>> and never interns again. The ServiceThread also concurrently grows the table if
>>> ‘load factor’ is high. Both the cleaning and growing take care to not prolonging
>>> time to safepoint, at the cost of some speed.
>>>
>>> Kitchensink24h, multiple tier1-5 with no issue that I can relate to this
>>> changeset, various benchmark such as JMH, specJBB2015.
>>>
>>> Issue: https://bugs.openjdk.java.net/browse/JDK-8195097
>>> Webrev: http://cr.openjdk.java.net/~rehn/8195097/v0/webrev/
>>>
>>> Thanks, Robbin
>