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https://issues.apache.org/jira/browse/HDFS-2243?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13106565#comment-13106565
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Hadoop QA commented on HDFS-2243:
---------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  
http://issues.apache.org/jira/secure/attachment/12494802/HDFS-2243-0.23-110909.patch
  against trunk revision .

    +1 @author.  The patch does not contain any @author tags.

    -1 tests included.  The patch doesn't appear to include any new or modified 
tests.
                        Please justify why no new tests are needed for this 
patch.
                        Also please list what manual steps were performed to 
verify this patch.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    +1 javac.  The applied patch does not increase the total number of javac 
compiler warnings.

    +1 findbugs.  The patch does not introduce any new Findbugs (version 1.3.9) 
warnings.

    +1 release audit.  The applied patch does not increase the total number of 
release audit warnings.

    -1 core tests.  The patch failed these unit tests:
                  org.apache.hadoop.hdfs.TestDfsOverAvroRpc
                  
org.apache.hadoop.hdfs.server.blockmanagement.TestHost2NodesMap

    +1 contrib tests.  The patch passed contrib unit tests.

Test results: 
https://builds.apache.org/job/PreCommit-HDFS-Build/1261//testReport/
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/1261//console

This message is automatically generated.

> DataXceiver per accept seems to be a bottleneck in HBase/YCSB test
> ------------------------------------------------------------------
>
>                 Key: HDFS-2243
>                 URL: https://issues.apache.org/jira/browse/HDFS-2243
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node
>    Affects Versions: 0.23.0
>         Environment: Using Fedora 14 on a quad core phenom system
>            Reporter: Eric Caspole
>            Priority: Minor
>             Fix For: 0.24.0
>
>         Attachments: HDFS-2234-branch-0.20-append.patch, 
> HDFS-2243-0.23-110909.patch, HDFS-2243-0.23-110909.txt, 
> datanode-perf-110808.gif
>
>
> I am running the YCSB benchmark against HBase, sometimes against a single 
> node, sometimes against a cluster of 6 systems. As the load increases into 
> thousands of TPS, especially on the single node, I can see that the datanode 
> runs very high system time and seems to be bottlenecked by how fast it can 
> create the threads to handle the new connections in DataXceiverServer.run. By 
> "perf top" I can see the process spends about 12% of all its time in 
> pthread_create, and in hprof profiles I can see there are tens of thousands 
> of threads created in just a few minutes of test execution.
> Does anyone else observe this bottleneck? Is there a major challenge to using 
> a thread pool of DataXceivers in this situation?

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