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

Robbin Ehn robbin.ehn at oracle.com
Thu Jun 7 09:58:17 UTC 2018

Thanks Jiangli!


On 2018-06-05 22:20, Jiangli Zhou wrote:
> Hi Robbin,
> The latest version looks good to me too!
> Thanks,
> Jiangli
>> On Jun 4, 2018, at 8:59 AM, Robbin Ehn <robbin.ehn at oracle.com> 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

More information about the hotspot-runtime-dev mailing list