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From "Jieshan Bean (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5088) A concurrency issue on SoftValueSortedMap
Date Mon, 26 Dec 2011 05:00:31 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5088?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13175887#comment-13175887
] 

Jieshan Bean commented on HBASE-5088:
-------------------------------------

@Ted,
At first, I also thought we would get a higher performance with this patch, because all the
keywords of "synchronized" removed. But it slowdown.
I agree with the explaination from Lars.
Our JDK version is 1.6.0_22. And the below is our OS information:
{noformat}
C3S3:~ # cat /proc/version
Linux version 2.6.32.12-0.7-default (geeko@buildhost) (gcc version 4.3.4 [gcc-4_         
                                   3-branch revision 152973] (SUSE Linux) ) #1 SMP 2010-05-20
11:14:20 +0200
C3S3:/proc # lsb_release -a
LSB Version:    core-2.0-noarch:core-3.2-noarch:core-4.0-noarch:core-2.0-x86_64:core-3.2-x86_64:core-4.0-x86_64:desktop-4.0-amd64:desktop-4.0-noarch:graphics-2.0-amd64:graphics-2.0-noarch:graphics-3.2-amd64:graphics-3.2-noarch:graphics-4.0-amd64:graphics-4.0-noarch
Distributor ID: SUSE LINUX
Description:    SUSE Linux Enterprise Server 11 (x86_64)
Release:        11
Codename:       n/a
{noformat}

We'll take more tests accross the read vs write and give out the results.

@Lars,
Sorry, I didn't do another comparison with SoftvalueSortedMap replaced by ConcurrentSkiplistMap.And
am planning to do it. Including the functional test and the performance test. And then, we
can choose a better one.
                
> A concurrency issue on SoftValueSortedMap
> -----------------------------------------
>
>                 Key: HBASE-5088
>                 URL: https://issues.apache.org/jira/browse/HBASE-5088
>             Project: HBase
>          Issue Type: Bug
>          Components: client
>    Affects Versions: 0.90.4, 0.94.0
>            Reporter: Jieshan Bean
>            Assignee: Jieshan Bean
>         Attachments: 5088-useMapInterfaces.txt, 5088.generics.txt, HBase-5088-90.patch,
HBase-5088-trunk.patch, HBase5088Reproduce.java
>
>
> SoftValueSortedMap is backed by a TreeMap. All the methods in this class are synchronized.
If we use this method to add/delete elements, it's ok.
> But in HConnectionManager#getCachedLocation, it use headMap to get a view from SoftValueSortedMap#internalMap.
Once we operate 
> on this view map(like add/delete) in other threads, a concurrency issue may occur.

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