documentation about performance and efficiency and caching

[David Crossley <cr...@apache.org>]

My current mission is to fine one of our Cocoon apps to deal with
an in-efficient document presentation job.

The various docs and wiki and cocoon.xconf and other config
seem a bit haphazard and conflicting, so i am trying to polish
them as i go.

One thing is the comment at:
http://wiki.cocoondev.org/Wiki.jsp?page=CocoonPerformance
<quote>
The advice in the cocoon.xconf file seems to suggest your store janitor
heapsize should be about 2% less than your max heap size (-Xmx setting).
...snip... seems high to me.
</quote>

What do they mean? Are our cocoon.xconf comments still correct?

--David

Re: documentation about performance and efficiency and caching

[Vadim Gritsenko <va...@reverycodes.com>]

David Crossley wrote:

>Carsten Ziegeler wrote:
><snip/>
>  
>
>>The last time I had to find memory leaks/problems for a customer
>>the values for the store janitor were wrong. At that time I
>>debugged the code and found out the above solution (2% less etc.).
>>And the settings worked very well. I think this is approx. eight
>>months ago, but I guess the comments in our xconf are still
>>appropriate.
>>    
>>
>
>Thanks for clarifying, i have removed the comment from the Wiki page.
>  
>

cocoon.xconf has (almost) correct comment:

      | It is recommended to have heapsize equal to -Xmx, especially on 
Sun's
      | JVM which are unable to shrink its heap once it grows above minimum.
      | Freememory should be greater than amount of memory necessary for 
normal
      | application operation.
      | BUT: The heap size of the memory of the JVM is a little bit less 
than
      |      the value you specify for -Xmx, so you have to set the heapsize
      |      for the store janitor to a value which is lower (2% less seems
      |      to be a working value).

It means, that when you specify -Xmx64m, Java will allocate 64Mb for the 
heap, but part of it will be utilized by Java internally, so heap as 
seen from the Java program will be smaller than 64Mb, at around 66600000 
bytes. Hence, you need to figure out "real" max heap size, which is a 
bit smaller (in this particular case, approx 2%) than 64Mb.

Vadim

RE: documentation about performance and efficiency and caching

[David Crossley <cr...@apache.org>]

Carsten Ziegeler wrote:
<snip/>
> The last time I had to find memory leaks/problems for a customer
> the values for the store janitor were wrong. At that time I
> debugged the code and found out the above solution (2% less etc.).
> And the settings worked very well. I think this is approx. eight
> months ago, but I guess the comments in our xconf are still
> appropriate.

Thanks for clarifying, i have removed the comment from the Wiki page.

--David

RE: documentation about performance and efficiency and caching

[Carsten Ziegeler <cz...@s-und-n.de>]

David Crossley wrote: 
> 
> My current mission is to fine one of our Cocoon apps to deal 
> with an in-efficient document presentation job.
> 
> The various docs and wiki and cocoon.xconf and other config 
> seem a bit haphazard and conflicting, so i am trying to 
> polish them as i go.
> 
> One thing is the comment at:
> http://wiki.cocoondev.org/Wiki.jsp?page=CocoonPerformance
> <quote>
> The advice in the cocoon.xconf file seems to suggest your 
> store janitor heapsize should be about 2% less than your max 
> heap size (-Xmx setting).
> ...snip... seems high to me.
> </quote>
> 
> What do they mean? Are our cocoon.xconf comments still correct?
> 
The last time I had to find memory leaks/problems for a customer
the values for the store janitor were wrong. At that time I
debugged the code and found out the above solution (2% less etc.).
And the settings worked very well. I think this is approx. eight
months ago, but I guess the comments in our xconf are still
appropriate.

Carsten