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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14268) Improve KeyLocker
Date Fri, 04 Sep 2015 03:50:45 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14268?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14730276#comment-14730276

stack commented on HBASE-14268:

Nice numbers. Out of interest, do you see weak references being collected in non-full GC?

Why do this and not just Iterate the passed in Set?

    Object[] keyArray = keys.toArray();

Why loop twice and not lock as you go: i.e. is this needed:

    for (Lock lock : locks.values()) {
97	      lock.lock();
134	    }	98	    }

I came across this: https://svn.apache.org/repos/asf/santuario/xml-security-java/trunk/src/main/java/org/apache/xml/security/utils/WeakObjectPool.java
 Might have some ideas you could make use of .

Yeah, good to call purge frequently doing references (at least that is what I've seen commonly
done -- our lrublockcache does simiilar).

Patch looks great.

There are other lock implementations in our code base. Woud be sweet if we could unify.

> Improve KeyLocker
> -----------------
>                 Key: HBASE-14268
>                 URL: https://issues.apache.org/jira/browse/HBASE-14268
>             Project: HBase
>          Issue Type: Improvement
>          Components: util
>            Reporter: Hiroshi Ikeda
>            Assignee: Hiroshi Ikeda
>            Priority: Minor
>             Fix For: 2.0.0, 1.3.0
>         Attachments: 14268-V5.patch, HBASE-14268-V2.patch, HBASE-14268-V3.patch, HBASE-14268-V4.patch,
HBASE-14268-V5.patch, HBASE-14268-V5.patch, HBASE-14268-V6.patch, HBASE-14268-V7.patch, HBASE-14268-V7.patch,
HBASE-14268.patch, KeyLockerPerformance.java
> 1. In the implementation of {{KeyLocker}} it uses atomic variables inside a synchronized
block, which doesn't make sense. Moreover, logic inside the synchronized block is not trivial
so that it makes less performance in heavy multi-threaded environment.
> 2. {{KeyLocker}} gives an instance of {{RentrantLock}} which is already locked, but it
doesn't follow the contract of {{ReentrantLock}} because you are not allowed to freely invoke
lock/unlock methods under that contract. That introduces a potential risk; Whenever you see
a variable of the type {{RentrantLock}}, you should pay attention to what the included instance
is coming from.

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