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From "Simone Tripodi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OGNL-20) Performance - Replace synchronized blocks with ReentrantReadWriteLock
Date Tue, 06 Sep 2011 13:31:09 GMT

    [ https://issues.apache.org/jira/browse/OGNL-20?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13097998#comment-13097998
] 

Simone Tripodi commented on OGNL-20:
------------------------------------

+1 to {{ReentrantReadWriteLocks}}.

IMHO

{code}
Map _methodParameterTypesCache = new HashMap();

synchronized (_methodParameterTypesCache)
{ 
    Class[] result; 

    if ( ( result = (Class[]) _methodParameterTypesCache.get( m )) == null )
    {
        _methodParameterTypesCache.put( m, result = m.getParameterTypes() ); 
    }
    return result; 
} 
{code}

and

{code}
Map _methodParameterTypesCache = new HashMap();

Class[] result; 

if ( ( result = (Class[]) _methodParameterTypesCache.get(m) ) == null )
{
    _methodParameterTypesCache.put( m, result = m.getParameterTypes() ); 
}
return result; 
{code}

have totally different semantics. In one case, you synchronized the whole block - including
the checks - in the second one, just limited the map accesses.
Am I wrong? If yes, why?

> Performance - Replace synchronized blocks with ReentrantReadWriteLock
> ---------------------------------------------------------------------
>
>                 Key: OGNL-20
>                 URL: https://issues.apache.org/jira/browse/OGNL-20
>             Project: OGNL
>          Issue Type: Improvement
>         Environment: ALL
>            Reporter: Greg Lively
>
> I've noticed a lot of synchronized blocks of code in OGNL. For the most part, these synchronized
blocks are controlling access to HashMaps, etc. I believe this could be done far better using
ReentrantReadWriteLocks. ReentrantReadWriteLock allows unlimited concurrent access, and single
threads only for writes. Perfect in an environment where the ratio of reads  is far higher
than writes; which is typically the scenario for caching. Plus the access control can be tuned
for reads and writes; not just a big synchronized{} wrapping a bunch of code.

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