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From "Jingcheng Du (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13702) Add a new instrumented read-write lock
Date Fri, 21 Oct 2016 03:17:58 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15593805#comment-15593805

Jingcheng Du commented on HADOOP-13702:

Thanks a lot [~chris.douglas].
bq. Shouldn't the ThreadLocal<Long> readLockHeldTimeStamp field be final, not transient?
Sorry for the careless, that was an old code for extending ReadLock which is serializable,
I only removed the readObject method but forgot this, so sorry.
bq. InstrumentedReadWriteLock could accept an instance of ReadWriteLock instead of creating
one. Similarly, the read/write locks could accept a ReadWriteLock in their constructor. IRWL
could also have the convenience constructor, as written.
The instrumented read lock uses methods in ReentrantReadWriteLock for instrumentation. If
we accept a ReadWriteLock in constructors i am afraid we cannot support the instrumentation
in the read lock.
bq. Is InstrumentedLock unused in HDFS? I expected to see package changes in the HDFS project
for the imports to resolve.
Only FsDatasetImpl uses this class, and this change is included in the patch:)

> Add a new instrumented read-write lock
> --------------------------------------
>                 Key: HADOOP-13702
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13702
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: common
>            Reporter: Jingcheng Du
>            Assignee: Jingcheng Du
>         Attachments: HADOOP-13702-V6.patch, HADOOP-13702-V7.patch, HADOOP-13702-V8.patch,
HDFS-10924-2.patch, HDFS-10924-3.patch, HDFS-10924-4.patch, HDFS-10924-5.patch, HDFS-10924.patch
> Add a new instrumented read-write lock in hadoop common, so that the HDFS-9668 can use
this to improve the locking in FsDatasetImpl

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