[jira] [Created] (HDFS-10804) Use finer-granularity lock for ReplicaMap

["Fenghua Hu (JIRA)" <ji...@apache.org>]

Fenghua Hu created HDFS-10804:
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             Summary: Use finer-granularity lock for ReplicaMap
                 Key: HDFS-10804
                 URL: https://issues.apache.org/jira/browse/HDFS-10804
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: hdfs
            Reporter: Fenghua Hu
            Assignee: Fenghua Hu
            Priority: Minor


In currently implementation, ReplicaMap takes an external object as lock for synchronization.

In function FsDatasetImpl#FsDatasetImpl(), the object is for synchronization is "this", i.e. FsDatasetImpl: 
volumeMap = new ReplicaMap(this);

and in private FsDatasetImpl#addVolume(), "this" object is used for synchronization as well.
ReplicaMap tempVolumeMap = new ReplicaMap(this);

I am not sure if we really need so big object FsDatasetImpl  for ReplicaMap's synchronization. If it's not necessary, this could reduce lock contention on FsDatasetImpl object and improve performance. 

Could you please give me some suggestions? Thanks a lot!

Fenghua



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