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From "Arpit Agarwal (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-10742) Measurement of lock held time in FsDatasetImpl
Date Wed, 07 Sep 2016 21:10:22 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10742?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15471815#comment-15471815
] 

Arpit Agarwal commented on HDFS-10742:
--------------------------------------

Thank you [~chris.douglas]. Your patch lgtm.
 
bq. I remain skeptical of AutoCloseableLock, since one could just use the Lock in interface
and existing tooling to implement the same. But if its virtues are obvious to everyone but
me I won't stand in the way of including it.
As you said its syntactic sugar. If this approach feels that inelegant I am okay with eliminating
{{AutoCloseableLock}}.

bq. Second, minutiae like "GC-friendliness", whether a wrapper class on Lock adds dispatch
overhead, class loading overhead, etc. when this JIRA logs critical sections longer than 300ms
are irrelevant, literally by orders of magnitude.
Moot point now but iiuc the object would have been allocated on every lock acquire whether
we logged or not. Perhaps the overhead would have been negligible but I'm not sure myself.

> Measurement of lock held time in FsDatasetImpl
> ----------------------------------------------
>
>                 Key: HDFS-10742
>                 URL: https://issues.apache.org/jira/browse/HDFS-10742
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode
>    Affects Versions: 3.0.0-alpha2
>            Reporter: Chen Liang
>            Assignee: Chen Liang
>         Attachments: HDFS-10742.001.patch, HDFS-10742.002.patch, HDFS-10742.003.patch,
HDFS-10742.004.patch, HDFS-10742.005.patch, HDFS-10742.006.patch, HDFS-10742.007.patch, HDFS-10742.008.patch,
HDFS-10742.009.patch, HDFS-10742.010.patch, HDFS-10742.011.patch, HDFS-10742.012.patch, HDFS-10742.013.patch,
HDFS-10742.014.patch, HDFS-10742.015.patch
>
>
> This JIRA proposes to measure the time the of lock of {{FsDatasetImpl}} is held by a
thread. Doing so will allow us to measure lock statistics.
> This can be done by extending the {{AutoCloseableLock}} lock object in {{FsDatasetImpl}}.
In the future we can also consider replacing the lock with a read-write lock.



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