[GitHub] sijie opened a new pull request #1299: [dlog] use Atomic***FieldUpdater and LongAdder if possible

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sijie opened a new pull request #1299: [dlog] use Atomic***FieldUpdater and LongAdder if possible
URL: https://github.com/apache/bookkeeper/pull/1299
 
 
   
   
   Descriptions of the changes in this PR:
   
   Atomic**FieldUpdater + volatile provides similar guarantees as Atomic*** but use much fewer memory.
   In dlog, when handling large number of streams, there can be a lot of Atomic*** fields with `LogHandler`, `SegmentWriter` and such.
   Switching using Atomic*** to using Atomic**FieldUpdater + volatile will save a lot of memory. See [details](http://normanmaurer.me/blog/2013/10/28/Lesser-known-concurrent-classes-Part-1/)
   
   LongAdder is less contended across threads, which is more preferable to AtomicLong when multiple threads update a common sum. E.g. SampledMovingAverageRate.
   Switching to use LongAdder if AtomicLong is not needed. See [details](https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/atomic/LongAdder.html)
   
   Master Issue: #<master-issue-number>
   
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