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From "Hiroshi Ikeda (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14268) Improve KeyLocker
Date Fri, 04 Sep 2015 01:30:45 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14268?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14730145#comment-14730145
] 

Hiroshi Ikeda commented on HBASE-14268:
---------------------------------------

I measured it just now in my environment, which has 8 cpu core, and the result is as followed.
For each KeyLocker I run the performance application 5 times and I collected the output number
which represents the consumed time (nanoseconds).

old KeyLocker
(1) 4168557944
(2) 4173845279
(3) 4276035366
(4) 4344219315
(5) 4393414763
average
= 4271214533.4 (nanos)
~ 4.27 (sec)

new KeyLocker
(1) 270832002
(2) 318058811
(3) 278171946
(4) 265603446
(5) 279867215
average
= 282506684 (nanos)
~ 0.28 (sec)

The difference just comes from overhead of context switches when getting/returning locks from/to
the pool, and this may be not so meaningful for heavy tasks which cause context switches.



> 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
>         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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