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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2243) DataXceiver per accept seems to be a bottleneck in HBase/YCSB test
Date Wed, 10 Aug 2011 20:18:27 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2243?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13082646#comment-13082646
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Todd Lipcon commented on HDFS-2243:
-----------------------------------

BTW, you may want to also look into SocketIOWithTimeout - I think we're doing some dumb things
with the way we use epoll, etc. I've tried to hack it out but couldn't quite get the NIO magic
right. Do you see epoll_wait taking a lot of systime?

> 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
>
> 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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