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https://issues.apache.org/jira/browse/OGNL-20?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13097998#comment-13097998
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Simone Tripodi edited comment on OGNL-20 at 9/6/11 1:30 PM:
------------------------------------------------------------
+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 ConcurrentHashMap();
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?
was (Author: simone.tripodi):
+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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