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From Leszek Gawron <lgaw...@mobilebox.pl>
Subject Re: Speed of jx-macros compared to FormsTransformer
Date Tue, 17 May 2005 18:13:05 GMT
Daniel Fagerstrom wrote:
> Reinhard Poetz wrote:
> 
>> Sylvain Wallez wrote:
> 
> 
> <snip/>
> 
>>> Ah no, forgot to say: this requires to use JXTemplate and the 
>>> forms-template-as-jx-macros.
>>
>>
>> Today I've run some load tests that compare Cocoon Forms using 
>> jx-macros and the FormsTransformer. The transformer is *considerably* 
>> faster (~ factor of 3!) than the macros and the higher the load the 
>> better for the transformer.
>>
>> Is there any special reason for this? 
> 
> 
> Macros has been reported to be slow before, IIRC. There is no reason 
> that they should be, maybe they not are cached as they should be? Leszek 
> has made the latest refactorings on the macros so he might have more 
> info. The template and the macros should be much faster the second time 
> they are execute, otherwise there is some problem with template caching. 
> Do you have any numbers on  that?
Let me outline some resource heavy operations operations that are 
performed in JXTG:

                    -o0 Parsing 0o-
Although costly this shouldn't in fact affect runtime - parsed templates 
are cached using transient store.

                    -o0 Imports 0o-
Imports are used mainly for separating macro definitions from template 
itself. Issues:

1. Template URI is resolved at runtime. We could skip this although this 
does not bring much overhead.

2. Parsed template is looked up for every run. This way we are aware of 
the fact that imported parts are invalidated and should be reparsed. If 
we store the reference to the template instead of looking it up we've 
got xsl:import case: you would have to touch main template in order to 
have imported template changes reparsed.

3. Imported file is executed for every template run. That is why you 
have a lot of whitespace in the output where you import external file.

4. Macro definitions are parsed at parse time but are REGISTERED in 
execution context during runtime 
(o.a.c.template.instruction.Define.execute inserts itself into the macro 
map in execution context). This is strictly connected with 2.: Changes 
in imported template have to be reflected somehow in execution context. 
Right now execution context is built from scratch every time.

5. I think that evaluating lot's of jexl/jxpath expressions is awfully 
costly. I was debugging jxpath with FOM_Request problem and it gave me 
shivers. There's not much really we can do about it.

6. Every element started in template is "suspected to be a macro call".

this means you can do:

<ft:widget id="something">
    <inner-content/>
</ft:widget>

instead of:
<jx:call macro="widget">
   <jx:withParam name="id" value="something">
   <inner-content/>
</jx:call>

but you make the invoker look up element's name in macro map for EVERY 
template element started. Costly as hell. JX instructions are resolved 
the same way but during parsing. We cannot do the same for macros 
because we do not know the full macros list at parsing time.


> Besides that does a lot of function calls through Jexl, that requires 
> reflection an might be costly.
> 
> Generally a large part of the work is done at compile time, so it should 
> at least in principle be efficient.
If we are to speed up things we need to drop the fine feature of 
automatic change detection in imported templates. Then:

1. Imports could be resolved at parse time/runtime depending on an 
attribute given. runtime imports generate content.

2. runtime import works as it is working now. it is not allowed to 
define macros there. I do not really know though if there should be such 
distinction.

3. parse time imports is only allowed to define macros and not produce 
content. Template will not be run so no whitespace would be produced.

4. Execution context is built up on template parsing. It contains a full 
list of expected macros.

5. <ft:widget id="something"> being a macro is being resolved at parse 
time, not runtime. A start element event is just a start element during 
runtime - never macro invocation.

Now I know why XSLT guys made xsl:import the way it is.

> But of course there can be bottle necks in different parts. We need 
> profiling info to know where to start optimizing. Do you have any 
> indication on where most of the time is spend?
> 
>> Any chance to speed up JX?
> 
> 
> Sure, give us profiling data ;)
We could always rewrite jx-macros.xml to Java which will fix performace 
problems for CForms (eliminating slow macro code and lots of 
reflection). Still there is no consensus about that issue and we still 
have a problem with other macros.

WDYT?
-- 
Leszek Gawron                                      lgawron@mobilebox.pl
IT Manager                                         MobileBox sp. z o.o.
+48 (61) 855 06 67                              http://www.mobilebox.pl
mobile: +48 (501) 720 812                       fax: +48 (61) 853 29 65

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