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https://issues.apache.org/jira/browse/HDFS-10804?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15528661#comment-15528661
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Fenghua Hu commented on HDFS-10804:
-----------------------------------
Thanks [~arpitagarwal] for updating the description to reflect the recent
changes in HDFS-10828. I updated a new version, could you please review it?
Note that I haven't change other places, i think if it's feasible, we will need
to change many places, for example:
we could safely remove datasetLock.acquire() from following code:
public FsVolumeImpl getVolume(final ExtendedBlock b) {
try (AutoCloseableLock lock = datasetLock.acquire()) {
final ReplicaInfo r =
volumeMap.get(b.getBlockPoolId(), b.getLocalBlock());
return r != null ? (FsVolumeImpl) r.getVolume() : null;
}
}
similar functions include: getStoredBlock() and some others functions which
uses lock for ReplicaMap exclusive access.
Once we agree to use separate lock for ReplicaMap, I'll modify them
correspondingly. It's expected to improve performance.
> Use separate lock for ReplicaMap
> --------------------------------
>
> Key: HDFS-10804
> URL: https://issues.apache.org/jira/browse/HDFS-10804
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs
> Affects Versions: 3.0.0-beta1
> Reporter: Fenghua Hu
> Assignee: Fenghua Hu
> Priority: Minor
> Attachments: HDFS-10804-001.patch, HDFS-10804-002.patch,
> HDFS-10804-003.patch
>
>
> In currently implementation, ReplicaMap takes an external lock for
> synchronization.
> In function FsDatasetImpl#FsDatasetImpl(), the object is for synchronization
> is the same lock object used by FsDatasetImpl routines.
> and in private FsDatasetImpl#addVolume(), the same lock is used for
> synchronization as well.
> {code}
> ReplicaMap tempVolumeMap = new ReplicaMap(datasetLock);
> {code}
> We can potentially eliminate the heavyweight lock for synchronizing
> ReplicaMap instances. If it's not necessary, this could reduce lock
> contention on the datasetLock object and improve performance.
> Could you please give me some suggestions? Thanks a lot!
> Fenghua
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