Ajay Sachdev commented on HADOOP-15471:

I have incorporated all items above. I am in process of putting some unit tests 
as well and testing these out. For number of threads option I have opted for -T 
<number of threads> in command line argument. The "du" command already had a 
lower -t option for storage type.

> Hdfs recursive listing operation is very slow
> ---------------------------------------------
>                 Key: HADOOP-15471
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15471
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs
>    Affects Versions: 2.7.1
>         Environment: HCFS file system where HDP 2.6.1 is connected to ECS 
> (Object Store).
>            Reporter: Ajay Sachdev
>            Assignee: Ajay Sachdev
>            Priority: Major
>             Fix For: 2.7.1
>         Attachments: HDFS-13398.001.patch, HDFS-13398.002.patch, 
> parallelfsPatch
> The hdfs dfs -ls -R command is sequential in nature and is very slow for a 
> HCFS system. We have seen around 6 mins for 40K directory/files structure.
> The proposal is to use multithreading approach to speed up recursive list, du 
> and count operations.
> We have tried a ForkJoinPool implementation to improve performance for 
> recursive listing operation.
> [https://github.com/jasoncwik/hadoop-release/tree/parallel-fs-cli]
> commit id : 
> 82387c8cd76c2e2761bd7f651122f83d45ae8876
> Another implementation is to use Java Executor Service to improve performance 
> to run listing operation in multiple threads in parallel. This has 
> significantly reduced the time to 40 secs from 6 mins.

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