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From Vadim Gritsenko <va...@reverycodes.com>
Subject Re: documentation about performance and efficiency and caching
Date Wed, 24 Mar 2004 13:02:35 GMT
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



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