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From "Chris Nauroth (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5049) Add JNI mlock support
Date Fri, 13 Sep 2013 17:28:52 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5049?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13766686#comment-13766686

Chris Nauroth commented on HDFS-5049:

Hi, [~andrew.wang].  I have a couple of questions on this patch related to use of {{getrlimit}}:

# Can you describe why it was necessary to round-trip {{rlim.rlim_curr}} through {{snprintf}}
to return a string from the native layer, and then parse it back to numeric in the Java layer?
 Would it be possible to return a {{jlong}} directly from the native layer?
# I'm wondering about handling of {{RLIM_INFINITY}}.  I don't know that this is guaranteed
to be a specific numerical value, so perhaps we need to skip the validation check in {{DataNode}}
if we get {{RLIM_INFINITY}}.
# {{getrlimit}} is not present on Windows, and AFAIK there is no equivalent.  Right now, the
HDFS-4949 branch won't compile on Windows.  I propose that we stub the implementation on Windows
to throw {{UnsupportedOperationException}} and checks to skip calling the method from Java
on Windows.  {{mlock}} and {{munlock}} appear to compile fine (yay POSIX!), though I'm not
yet sure if they work as expected on Windows or if we really would need to call {{VirtualLock}}/{{VirtualUnlock}}.
 We can figure that out later.  Right now, I'm mostly just interested in making sure the branch
compiles on Windows.

Let me know your thoughts.  I can file follow-up jiras as appropriate.  Thanks!

> Add JNI mlock support
> ---------------------
>                 Key: HDFS-5049
>                 URL: https://issues.apache.org/jira/browse/HDFS-5049
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: datanode, namenode
>            Reporter: Colin Patrick McCabe
>            Assignee: Andrew Wang
>         Attachments: hdfs-5049-1.patch
> Add support for {{mlock}} and {{munlock}}, for use in caching.

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