Re: Optimising Variable to reduce instantiation overhead

On Sun 12 March 2006 21:14, Lane Sharman wrote:
> alex,
>
> thanks for this improvement and catch. Are there any issues or concerns you
> have with this proposed update?

none that I can see - there is a very slight performance hit checking to see 
whether or not _vname has been initialised inside getVariableName() (along 
with the synchronized lock acquisition), but this is only ever invoked while 
constructing a PropertyException which has such a huge overhead from building 
the stack trace that it is irrelevant.

The only potential problem is that there are some 3rd party extensions of 
Variable that aren't included in the standard ant build which might break by 
making _vname private, but these are easily refactored to use the method call 
instead.

Alex

ps I posted some patches to the list to make Broker shutdown cleanly and 
ensure that webmacro applications unload cleanly when reloading under tomcat.  
I was about 20k over the list limit, and am in a blocking queue.  Do you know 
who is the list admin to let this through, or should I repost with the fixes 
chopped into smaller amounts?

> Lane
>
> --- [email protected] wrote:
>
> From: Alex Twisleton-Wykeham-Fiennes <[email protected]>
> To: [email protected]
> Subject: [WebMacro-user] Optimising Variable to reduce instantiation
> overhead Date: Sun, 12 Mar 2006 18:50:17 +0000
>
> All,
>
> more performance tweaks, this one to the org.webmacro.engine.Variable
> class.
>
> performance sampling showed a large proportion of CPU time being allocated
> to the makeName(Object[] names) class that is invoked in the constructor to
> create the human-readable version of the Object[] that stores the names,
> which is then stored in _vname.
>
> However, _vname is only ever used in situations when you generating
> PropertyException Objects to provide sensible error messages, and for all
> "correctly functioning" instances, this is completely redundant.
>
> What I've done is:-
>
> - disabled the call to makeName(names) in the constructor
> - made the getVariableName() method check to see if _vname has been
> initialised, and if not then build the name before returning it.  This is
> now synchronized as it changes the state of the object.
> - made all previous references to _vname in the Variable class invoke
> getVariableName() rather than accessing the variable directly.
> - made _vname private rather than protected thereby forcing sub-classes to
> access it via getVariableName()
>
> The resulting class (attached) passes all the unit tests and completely
> removes this overhead for all normal usage patterns.
>
> Alex
>
>
>
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