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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-5366) recaching improvements
Date Tue, 12 Nov 2013 23:21:17 GMT

     [ https://issues.apache.org/jira/browse/HDFS-5366?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Colin Patrick McCabe updated HDFS-5366:
---------------------------------------

    Attachment: HDFS-5366.005.patch

I found that in order to create an effective test, I needed some way of injecting code into
the mlock calls.  So I created {{NativeIO#CacheManipulator}} for this purpose.  This made
the patch a little bigger but I think it's worth it.  Hopefully this will also resolve issues
with mlock failing with ENOMEM when tests are run concurrently, etc.

> recaching improvements
> ----------------------
>
>                 Key: HDFS-5366
>                 URL: https://issues.apache.org/jira/browse/HDFS-5366
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: namenode
>    Affects Versions: 3.0.0
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>         Attachments: HDFS-5366-caching.001.patch, HDFS-5366.002.patch, HDFS-5366.005.patch
>
>
> There are a few things about our HDFS-4949 recaching strategy that could be improved.
> * We should monitor the DN's maximum and current mlock'ed memory consumption levels,
so that we don't ask the DN to do stuff it can't.
> * We should not try to initiate caching on stale or decomissioning DataNodes (although
we should not recache things stored on such nodes until they're declared dead).
> * We might want to resend the {{DNA_CACHE}} or {{DNA_UNCACHE}} command a few times before
giving up.  Currently, we only send it once.



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