[jira] Commented: (HADOOP-4752) Major performance drop on slower machines

["Craig Macdonald (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-4752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12661292#action_12661292 ] 

Craig Macdonald commented on HADOOP-4752:
-----------------------------------------

I did some timings in HADOOP-4 - my test network machines were quite dated. Comparing fuse_dfs with bin/hadoop fs -cat (and NFS),  showed that fuse_dfs was distinctly slower - almost half the speed.

I think that we should test libhdfs, as this would show if the penalty is the JNI, or fuse_dfs.

I've recently documented some thoughts in HADOOP-4932 concerning the doConnectAsUser in fuse_dfs, but I realise now that this partly echoes Marc-Olivier's thoughts.



> Major performance drop on slower machines
> -----------------------------------------
>
>                 Key: HADOOP-4752
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4752
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: contrib/fuse-dfs
>    Affects Versions: 0.18.2
>            Reporter: Marc-Olivier Fleury
>
> When running fuse_dfs on machines that have different CPU characteristics, I noticed that the performance of fuse_dfs is very sensitive to the machine power. 
> The command I used was simply a cat over a rather large amount of data stored on HDFS. Here are the comparative times for the different types of machines:
> Intel(R) Pentium(R) 4 CPU 2.40GHz :                                2 min 40 s 
> Intel(R) Pentium(R) 4 CPU 3.06GHz:                                 1 min 50 s 
> 2 x Intel(R) Pentium(R) 4 CPU 3.00GHz:                           0 min 40 s 
> 2 x Intel(R) Xeon(TM) MP CPU 3.33GHz:                           0 min 28 s 
> Intel(R) Core(TM)2 Quad CPU    Q6600  @ 2.40GHz      0 min 15 s
> I tried to find other explanations for the drop in performance, such as network configuration, or data locality, but the faster machines are the ones that are "further away" from the others considering the network configuration, and that don't run datanodes.
> top shows that the CPU usage of fuse_dfs is between 80-90% on the slower machines, and about 40% on the fastest one.
> This leads me to the conclusion that fuse_dfs consumes a lot of CPU resources, much more than expected.
> Any help or insight concerning this issue will be greatly appreciated, since these difference actually result in days of computations for a given job.
> Thank you

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